Mini automatic transfer switch

ABSTRACT

An automatic transfer switch (100) for automatically switching an electrical load between two power sources is provided. Two power cords (106) enter the ATS (A power and B power inputs) and one cord (109) exits the ATS (power out to the load). The ATS has indicators (107) located beneath a clear crenelated plastic lens (108) that also acts as the air inlets. The ATS (100) also has a communication portal (103) and a small push-button (104) used for inputting some local control commands directly to the ATS (100). The ATS (100) can be mounted on a DIN rail at a rack and avoids occupying rack shelves.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Nos.63/063,966 and 63/064,361, both entitled “INDUSTRIAL AUTOMATIC TRANSFERSWITCH” and filed on Aug. 11, 2020. This Application also ClaimsPriority to U.S. patent application Ser. No. 16/817,504, entitled,“RELAY CONDITIONING AND POWER SURGE CONTROL,” filed Mar. 12, 2020, whichclaims priority from U.S. Provisional Patent Application Ser. No.62/817,456 of the same title filed on Mar. 12, 2019. This applicationfurther claims priority to U.S. patent application Ser. No. 17/093,485entitled “INTELLIGENT AUTOMATIC TRANSFER SWITCH MODULE,” filed Nov. 9,2020, which is a continuation of Ser. No. 16/351,431, entitled,“MANAGEMENT MODULE, Z-STRIP, AND MINI-ATS SYSTEMS AND RELATEDCOMPONENTS,” filed on Mar. 12, 2019, which claims priority from U.S.Provisional Application No. 62/641,943, entitled, “POWER DISTRIBUTIONUSING HYDRA CABLE SYSTEMS,” filed on Mar. 12, 2018, and U.S. ProvisionalApplication No. 62/641,929, entitled, “MANAGEMENT MODULE, Z-STRIP, ANDMINI-ATS SYSTEMS AND RELATED COMPONENTS,” filed on Mar. 12, 2018. ThisApplication also claims priority to U.S. patent application Ser. No.16/351,343, entitled, “POWER DISTRIBUTION USING HYDRA CABLE SYSTEMS,”filed on Mar. 12, 2019, and PCT Application No. PCT/US2019/021936,entitled, “MANAGEMENT MODULE, Z-STRIP, AND MINI-ATS SYSTEMS AND RELATEDCOMPONENTS,” filed on Mar. 12, 2019. The contents of the above-notedapplications (collectively, the “parent applications”) are incorporatedby reference herein as if set forth in full and priority to theseapplications are claimed to the full extent allowable under U.S. law andregulations.

INCORPORATION BY REFERENCE

The systems, components and processes described herein build on and canbe combined with a number of technologies of Zonit Structural Solutions(Zonit) to yield synergies or combinative advantages such as improvedefficiency of rack space, reduced rack size for a given payload ofequipment, enhanced functionality, enhanced networking and monitoring ofequipment, reduced equipment requirements and costs, and others.Accordingly, reference is made at various points in the description toone or more of the following families of U.S. cases (patents andapplications) of Zonit (it is intended to reference all related U.S.application and patents in each family that are available to beincorporated by reference), all of which are incorporated by referenceherein in their entireties.

1. U.S. Pat. Appl. Ser. Nos. 60/894,842; 12/049,130; 12/531,212;12/569,733 (the ATS cases);

2. U.S. Pat. Appl. Ser. Nos. 60/894,844; 12/531,215; 13/889,181;15/353,590; 14/217,225 (the Z-cool cases);

3. U.S. Pat. Appl. Ser. Nos. 60/894,846; 12/531,226; 12/569,377;13/757,156; 13/763,480; 14/717,899; 15/655,620; 15/656,229 (the SmartOutlets cases);

4. U.S. Pat. Appl. Ser. Nos. 60/894,848; 12/531,231; 12/569,745;13/466,950; 14/249,151; 13/208,333; 14/191,339; 14/564,489; 15/603,217;15/797,756; 61/970,267; 61/372,752; 61/372,756; 13/208,333; 61/769,688;14/191,339; 14/564,489; 15/603,217; 15/797,756 (the Auto-Switchingcases);

5. U.S. Pat. Appl. Ser. Nos. 61/324,557; 13/088,234; 14/217,278;15/250,523; 15/914,877; 60/894,849; 12/531,235; 12/568,444; 13/228,331;61/610,183; 61/619,137; 61/799,971; 61/944,506; 15/064,368; 15/332,878(the Locking Receptacle cases);

6. U.S. Pat. Appl. Ser. Nos. 60/894,850; 12/531,240; 12/569,609;14/470,691; 15/673,153 (the NetStrip cases);

7. U.S. Pat. Appl. Ser. Nos. 61/039,716; 12/891,500; 13/108,824;14/217,204; 14/680,802; 15/450,281 (the Power Distribution Methodologycases);

8. U.S. Pat. Appl. Ser. Nos. 61/040,542; 12/892,009; 13/108,838;14/327,212 (the UCAB cases);

9. U.S. patent application Ser. No. 09/680,670 (the ZPDS case);

10. U.S. Pat. Appl. Ser. Nos. 14/217,159; 15/452,917; 14/217,172;15/425,831; 14/217,179; 15/706,368 (the Relay cases);

The parent cases together with the other cases noted above areoccasionally referred to collectively herein as the Zonit cases.

BACKGROUND

Electronic data processing (EDP) equipment, such as servers, storagedevices, or the like, are often fed by alternating current (AC) powersources in a data center and require very high reliability. For thisreason, this equipment is generally fed by one or more uninterruptiblepower sources (UPS). When redundant power sources (e.g., A and B powersources) are supplied in a data center, the data center manager mustmanage the provisioning and capacity demand for both of the sources. Theprovisioning must be done so that if either of the two sources fails,the remaining power source has sufficient power capacity to carry thetotal load of the equipment. However, the complexity of delivering powerfrom a UPS to the equipment often creates numerous possibilities forinterruption. For example, power distribution circuits, interim circuitbreakers, plugboards, power whips, power distribution units (PDUs),power strips, power cords (often non-locking), and other distributionelements are often placed in the circuit path between large UPS systemsand the EDP equipment. These components increase the probability of aninterruption or disconnection of the equipment from the power sources.EDP equipment may contain a dual power supply arrangement that canprovide direct current (DC) power to the internal circuits of theequipment from two separate AC sources. Also, UPS systems and otherpower distribution components need maintenance which may require thatthey be taken out of service.

In this arrangement, the failure of one of the AC sources will result inthe equipment load being supplied from the alternate DC power supply inthe unit. At times when both AC sources are present, the load is eithershared by both power supplies, or favored to one of the power supplies.These systems, sometimes referred to as “redundant supplied” systems,may be a final line of defense for reliable power delivery to theelectronic circuits within the equipment. However, these solutions maybe costly due to the additional power supplies that may be required.Further, the added components generate more heat, which is undesirablein many applications. Alternatively, EDP equipment may include only onepower supply and one AC power input. In this configuration, theequipment is subject to the failure of the single AC source. Further,additional components such as Automatic Transfer Switches to addressthis vulnerability may require rack space, which is costly.

Aggregating a plurality of such affected EDP equipment onto a multipleoutlet power distribution unit (PDU) and powering that PDU from aswitching apparatus such as an Automatic Transfer Switch (ATS) thatselects from the available power sources (e.g. A or B) is an alternativemeans of delivering redundant power to said EDP equipment while reducingthe number of power supplies, cords, etc. It may be a superior methoddue to cost and efficiency for many deployment scenarios, such as largeserver farms for example.

In another application, many industrial devices starting in the 1960'shave incorporated intelligent control modules using digital processingcomponents, for example, one or more single chip microcontrollers (MCU)or other digital processing components. The Intel 8051 is a famous andwidely used example of this type of component. These components havegained greatly in computing power and capability, accelerated by thecell phone revolution which for example uses many ARM-32 & ARM-64 MCUcomponents. The increase in computing power of these components hasallowed significant increases in the complexity and capability of theprogramming logic they execute. Insuring that intelligent controlmodules have maximum uptime delivers many benefits. Many failures oflong-service time modules occur at power-up. So, avoiding unnecessaryreboot or restart cycles improves reliability. Many software algorithmsused with control modules “learn” as runtime increases and some or allof that learning may be lost when the module is rebooted due to powerdistribution maintenance, UPS maintenance, UPS failure or a power sourcefailure. The use of an appropriate ATS unit in the power path to theintelligent control module(s) in these industrial devices can eliminatethese potential problems and maximize uptime.

It should be realized that laptop/desktop/server computers, single boardcomputers (SBC), system-on-a-chip (SOC), Microcontroller units (MCUs),and other similar components that are all essentially digital devicescapable of executing programs. Further SBC units, SOC, MCU and othersimilar digital processing components are rarely built into computingdevices that are designed with dual power supplies. All of thesecomputing devices can run programs that can benefit from improveduptime, by properly using appropriate Automatic Transfer Switch units asdescribed herein. The uptime benefits are obvious for any digitalprocessing device with a single power supply, but also can benefitdigital processing devices that have dual power supplies.

It is against this background that the automatic transfer switch moduledescribed herein has been developed.

SUMMARY

The following embodiments and aspects of the invention herein aredescribed and illustrated in conjunction with systems, tools, andmethods which are meant to be exemplary and illustrative, and notlimiting in scope.

In accordance with one instantiation of the current invention, anautomatic transfer switch for automatically switching an electrical loadbetween two power sources is provided. The automatic transfer switchincludes a switch module, and primary and secondary input cords, eachattached to the switch module, and each for receiving power from adifferent one of the two power sources. For use in data centerenvironments with A-B power sources, it is desirable todeterministically manage the load on the A and B power sources. Theautomatic transfer switch may be operable to prefer and use the A powersource (i.e., primary power source) when it is available and only usethe B power source (i.e., secondary power source) when the A powersource is unavailable. Conversely, the automatic transfer switch may beoperable to prefer and use the B power source (i.e., primary powersource) when it is available and only use the A power source (i.e.,secondary power source) when the B power source is unavailable. Forexample, the source that has the desired voltage or any other powerquality characteristic or combination of characteristics that is bestsuited for the EDP equipment load being fed may be preferred as thedesired source. The automatic transfer switch can also make thesedeterminations of power source preference based not only onavailability, but also on the quality of the power. The ATS may bedesigned to allow the data center manager to choose which power input isthe preferred input. This may be done by explicit interaction with theATS unit (by a manual power input selector, graphical user interfaceobject, or other user control for example), automatically (e.g., inresponse to a sensed electrical condition or environmental sensor input)or by remote control via remote EDP apparatus, for example the Zonitcontrol module as is described below. This is desirable so that the datacenter manager can allocate power distribution system capacity withcontrol and assurance of what source will normally feed those connectedloads. The automatic transfer switch can also make these choices aboutwhat power source to prefer based not only the availability, but also onthe quality of the input power. For example, the source that has thevoltage or any other power quality characteristic or combination ofcharacteristics that is best suited for the EDP equipment load being fedmay be preferred as the desired source.

The automatic transfer switch also includes an output cord (or one ormore output receptacles) attached to the switch module, for supplyingpower to the electrical load. Additionally, the automatic transferswitch can include one or more relays (e.g., mechanical relays,solid-state relays, or a combination of both) disposed within the switchmodule and coupled to the primary input cord. The relay is operable tosense suitable power delivery characteristics (i.e., quality) on theinput cords and automatically couple the output cord to either theprimary or secondary input cords in accordance with one or more valuesof the input power quality.

The automatic transfer switch also may have one or more communicationsmechanisms that allow it to be connected to remote EDP apparatus (suchas the Zonit control module for example) enabling monitoring, control(including configuration) and reporting of the automatic transfer switchvia remote and/or local electronic means. This can enable reporting ofany power quality characteristic measured or observed at the ATS, thestatus of connected EDP equipment and any power quality characteristicthat the EPD equipment load(s) affects. It can also include othervariables such as the hardware and software health and internalenvironmental conditions of the ATS unit or a connected device withappropriate apparatus. Any other information that is desired about theATS unit and its components for example cooling fan performance andstatus could be supplied. If desired the ATS unit can be equipped withconnections for additional sensors such as environmental (temperature,humidity, moisture present, smoke detection), safety (door lock status,moisture present, smoke detection), or other sensor type as needed. TheATS unit can provide the information needed to do electrical usagemeasurement and billing functions if desired. The ATS unit can reportany or all the information gathered to the remote EDP apparatus asneeded and desired, where it can be processed, displayed and acted uponas desired. Alternatively, the ATS unit can process the information andtake actions, generate alerts or use other status information fordisplay by the ATS unit as desired.

The ATS unit can incorporate the ability to sample the waveform of oneor more power inputs and/or the power output of the ATS in highresolution, in one instantiation 15 kHz. An example circuit to do thiswhich can be constructed in a small space, with a low power budget, forvery low cost, (which makes it possible to incorporate in any of theinventions and their possible instantiations described herein) isdescribed later. This sampling rate is sufficient to provide verydetailed information on the power quality of the input source(s) and/orthe connected output load or loads. This level of sampling isfunctionally similar to high-quality dedicated power quality analysisinstruments such as offered by Fluke, Tektronics, and othermanufacturers. Additionally, this same level of power qualitymeasurement can be embedded as an optional capability into the powerdistribution devices described in the Zonit cases which are incorporatedby reference herein. Having this level of power quality measurementembedded into the power distribution system of a data center, factory,office, or home allows a wide range of capability as described in theZonit cases.

The automatic transfer switch may be implemented in a relatively smalldevice that is suitable for deployment in less than a full 1U of rackmounting space or adjacent to rack mounted electrical devices orsimilarly to a PDU associated with those electrical devices. It may beused in any structure suitable for supporting electrical devices (e.g.,2 post equipment racks, 4 post equipment racks, various types ofcabinets, or the like). It may be mounted in a partial 1U space that isalready partially used by EDP equipment (thus not sacrificing any 1Urack spaces) or in parts of the rack that are not used when mounting. Insome instantiations, the switch module may occupy less than 85 cubicinches, for single-phase configurations and 150 cubic inches forthree-phase configurations. In this regard, the automatic transferswitch is likely to not require mounting space in an equipment rack, andthis may reduce cooling problems that are associated with sizablecomponents and longer power cords used in traditional designs. Theswitch may also consume relatively little power (less than 2 Watts insome instantiations) compared to other automatic transfer switches, dueto the use of modern solid-state components and innovative design.

There are multiple instantiations of the automatic transfer switch thatcan be created, depending on the needs and requirements of theapplication. A variety of possible instantiations are shown in FIGS.18-20. Some of the instantiations can be either single-phase orpolyphase power ATS units. The instantiations have a variety of possibleform-factors, some of which are capable of zero-U mounting, some ofwhich are rack-mountable, and some which are sufficiently small to beconveniently embedded in an industrial device, such as a control moduleenclosure or cabinet for that industrial device, as described in moredetail in the Zonit cases. This small size factor is very important;rack-mounted ATS units can be difficult or impossible to integrate inmany types of applications. Some of the instantiations may have featuressuitable for industrial device usage, such as DIN rail mountingcompatibility, either by having the integral slots in the case accept astandard dimension DIN rail or by use of a DIN rail adapter, which canmount to the integral slots. Some instantiations of the ATS units mayincorporate terminal blocks rather than input and/or output cords orreceptacles, since this can make it more convenient to connect the ATSunit to the wiring harness of the industrial device or otherapplication.

In accordance with another aspect of the present invention, an automatictransfer switch for automatically switching an electrical load betweentwo power sources is provided. The automatic transfer switch includes aswitch module that occupies less than 85 cubic inches of space. Theautomatic transfer switch also includes primary and secondary inputcords, each attached to the switch module, and each for receiving powerfrom a different one of the two power sources, and an output cord thatis attached to the switch module for supplying power to the electricalload, or to a PDU capable of supplying power to a plurality of EDPequipment loads. Additionally, the automatic transfer switch includesone or more relays contained within the switch module and having avoltage sensitive input coupled to the primary input cord for couplingthe output cord to the primary input cord when one or more powerqualities of the primary input cord is acceptable, and for coupling theoutput cord to the secondary input cord when one or more power qualitieson the primary input cord are not acceptable. Additionally, the primarysource and the secondary source are selectable with regards to which isassigned to the physical “A” and “B” inputs of the automatic transferswitch.

In accordance with another aspect of the present invention, an automatictransfer switch, (the Zonit μATS-Mini™ is one possible example while theZonit μATS-Industrial™ has a somewhat larger spatial envelope) forautomatically switching an electrical load between two power sources isprovided. The automatic transfer switch includes a switch module thatoccupies less than 150 cubic inches of space. It can be provided in arange of amperage capacities as needed, but still be small enough toeasily be mounted in an industrial control enclosure or cabinet. It canbe DIN rail mounted, either directly or via an adapter. It can have avery high MTBF and a wide operational temperature range, suitable forindustrial device environments. The automatic transfer switch alsoincludes primary and secondary input cords, each attached to the switchmodule, and each for receiving power from a different one of the twopower sources, and an output cord that is attached to the switch modulefor supplying power to the electrical load, or optionally a terminalblock for the input and output power connections. Additionally, theautomatic transfer switch includes one or more relays contained withinthe switch module and having a voltage sensitive input coupled to theprimary input cord for coupling the output cord to the primary inputcord when one or more power qualities of the primary input cord isacceptable, and for coupling the output cord to the secondary input cordwhen one or more power qualities on the primary input cord are notacceptable. The relays can be designed to be open when the control logicis not operational, which is the default for most ATS units. Thisensures that if there is a logic problem with the ATS unit it does notdeliver power. Additionally, the primary source and the secondary sourceare both capable of powering the unit up if only one is energized. Theunit can be equipped with either fuses and a Virtual Circuit Breakerw/reset button (as described in the Zonit cases incorporated byreference in full) or one or more small-form factor circuit breakers. Inthis way protection against overloads is provided. Each method hasadvantages.

The automatic transfer switch can be provided with clearly visiblestatus indicator lights that can be viewed regardless of the angle ororientation of the automatic transfer switch. This allows a wide varietyof mechanical mounting configurations without interfering withvisibility of said status indicators. The status indicator lights can bemirrored to or replicated by a remote display and/or to the remotemanagement device(s) as desired, to be displayed as needed. The statusindicator lights can indicate which power input source is currentlybeing used. They can also indicate whether the unused power source ispresent and/or of suitable quality. This can be done by controlling theintensity, blink rate, pattern or other visible parameter of theindicator lights. The ATS unit can also incorporate Zonit ZCrushcircuitry to prevent discharge of stored energy from the connected loadsthrough the ATS unit when the ATS unit is performing a power sourcetransfer. A number of examples of this phenomenon are discussed in U.S.patent application Ser. No. 16/817,504 entitled “Relay Conditioning andPower Surge Control,” filed on Mar. 12, 2020, (the ZCrush case) which isincorporated herein by reference. A common practice in industrialcontrol modules is to use a large filter capacitor across the AC maininputs (similar to what is done in AC/DC power supplies as discussed inthe ZCrush case) and/or step down the AC voltage to 24 or 48 volts via atransformer that often can store a large amount of energy in its corewhich can be discharged through the ATS unit when a power transferoccurs. The ATS unit can also be auto-ranging, that is operate on a widerange of input voltages for example 24-277V, 48-277V, 80-277V or otherdesired voltage operating ranges. The unit can be designed to work witheither DC or AC power.

In accordance with another aspect of the present invention, an automatictransfer switch, (the Zonit μATS-V2™ is one possible example) forautomatically switching an electrical load between two power sources isprovided. The automatic transfer switch includes a switch module thatoccupies less than 150 cubic inches of space. It can be provided in arange of amperage capacities as needed, but still be small enough toeasily be mounted in an EDP equipment rack or cabinet. It can be DINrail mounted, either directly or via an adapter in the cabinet. Theautomatic transfer switch also includes primary and secondary inputcords, each attached to the switch module, and each for receiving powerfrom a different one of the two power sources, and an output cord thatis attached to the switch module for supplying power to the electricalload. Additionally, the automatic transfer switch includes one or morerelays contained within the switch module and having a voltage sensitiveinput coupled to the primary input cord for coupling the output cord tothe primary input cord when one or more power qualities of the primaryinput cord is acceptable, and for coupling the output cord to thesecondary input cord when one or more power qualities on the primaryinput cord are not acceptable. The relays can be designed to be closedwhen the control logic is not operational, which is not the default formost ATS units. This ensures that if there is a logic problem with theATS unit it does continue to deliver power. Additionally, the primarysource and the secondary source are both capable of powering the unit upif only one is energized.

The unit can be equipped with both fuses and a Virtual Circuit Breakerw/reset button (as described in the Zonit cases which are incorporatedby reference in full). This is compatible with failing closed if the ATScontrol logic fails, since in that case, the unit becomes a fused powercord on the side that is connected when the relays are not powered andclosed. In this way protection against overloads is provided, regardlessif the control logic is functional or not. The automatic transfer switchcan be provided with clearly visible status indicator lights that can beviewed regardless of the angle or orientation of the automatic transferswitch. This allows a wide variety of mechanical mounting configurationswithout interfering with visibility of said status indicators. Thestatus indicator lights can be mirrored to or replicated by a remotedisplay and/or to the remote management device(s) as desired, to bedisplayed as needed. The status indicator lights can indicate whichpower input source is currently being used. They can also display is theunused power source is present. This can be done by controlling theintensity, blink rate, pattern or other visible parameter of theindicator lights. The indicator lights can also indicate if there is apower quality problem or the amperage being delivered exceeds a givenpercentage of the capacity of the ATS unit. This is useful in datacenter loads where EDP equipment is moved into and out of racks and thepower delivered by the ATS unit can thereby vary. It helps data centerstaff not overload the ATS unit. The ATS unit can also incorporate ZonitZCrush circuitry to prevent discharge of stored energy from theconnected loads through the ATS unit when the ATS unit is performing apower source transfer. A number of examples of this phenomenon arediscussed in the ZCrush case which is incorporated by reference. The ATSunit can also be auto-ranging, that is operate on a wide range of inputvoltages for example 24-277V, 48-277V, 80-277V or other desired voltageoperating ranges.

According to a still further aspect of the present invention, a methodfor use in providing power to an electrical device is provided. Themethod includes providing an auto-switching device having a firstinterface for coupling to a first power source, a second interface forcoupling to a second power source, and one or more third interfaces forcoupling to the electrical device to be powered. The auto-switchingdevice is operative to automatically switch between the first and secondpower sources in response to an interruption of the quality of theprimary input power. The method also includes coupling the firstinterface to the first power source, coupling the second interface tothe second power source, coupling the third interface(s) to theelectrical device and selecting one of the first and second powersources as the primary source. Additionally, the automatic transferswitch, being connected via electronic means to remote managementequipment, can also serve to turn off or on power to the equipmentconnected to the output of the automatic transfer switch in response toeither manual operator desire, or automatically in the event ofover-temperature, or fire/smoke detection, or any number of otherconditions deemed necessary by the remote controlling equipment and anyattached sensor devices monitorable by said remote controllingequipment.

Additionally, the automatic transfer switch has clearly visible statusindicator lights that can be viewed regardless of the angle ororientation of the automatic transfer switch. This allows a wide varietyof mechanical mounting configurations without interfering withvisibility of status indicators.

Additionally, the automatic transfer switch module can incorporateunique mounting slots that ease the burden of physically and securelymounting the automatic transfer switch module to a secure mountinglocation. The unique slots allow use of a variety of standardoff-the-shelf hardware combinations to attach to the automatic transferswitch module easily and without special adapters or tools.

According to a still further aspect of the present invention, a systemfor powering a rack mounted electrical device is provided. The systemincludes a rack or cabinet that has a plurality of power sources.Further, the system includes an auto-switching module including a firstcord coupled to the first power source, a second cord coupled to thesecond power source, and one or more third cord(s) coupled to anelectrical device supported on one of the shelves of or otherwisemounted to the rack or to a power distribution unit (such as ahorizontal or vertically mounted plugstrip or powerstrip) capable ofdelivering power from the output of the automatic transfer switch to aplurality of equipment. The auto-switching module is operative to switcha supply of power to the electrical device(s) between the first andsecond power sources in response to an interruption on the current inputsource or other power quality characteristic of the input power.Additionally, the automatic transfer switch, via local or remote means(by connection to remote management devices), can also serve to turn offor on power to the equipment connected to the output of the automatictransfer switch in response to either an explicit operator request(e.g., entered by a user employing a physical selector, such as a buttonor switch, or employing an electronic sensor such as an object of agraphical user interface), or automatically in the event ofover-temperature, or fire/smoke detection, or any number of otherconditions deemed necessary, either by the ATS unit or by the remotecontrolling equipment and the attached sensory devices of each. The ATSmay also include a current limiting device for limiting the maximumcurrent across the device to remain within a defined range.

The automatic transfer switch has clearly visible status indicatorlights that can be viewed regardless of the angle or orientation of theautomatic transfer switch. This allows a wide variety of mechanicalmounting configurations without interfering with visibility of saidstatus indicators. The status indicator lights can be mirrored to orreplicated by a remote display and/or to the remote management device(s)as desired, to be displayed as needed. The housing may also includeslots or other openings for dissipating heat generated by the ATS.

The automatic transfer switch module can be provided with uniquemounting slots as part of its enclosure that ease the task of physicallyand securely mounting the automatic transfer switch module in a securemounting location. The unique slots allow use of a variety of standardoff-the-shelf hardware combinations to attach to the automatic transferswitch module easily and without special adapters or tools.

The solutions we have invented are innovative and provide considerablebenefits. They include a number of electronic circuits that performvarious functions. We describe below their usage in the context of anautomatic transfer switch, but they may also be useful in otherapplications. The automatic transfer switch we are using as adescriptive example can incorporate the inventions described in PCTApplication No. PCT/US2008/057140, U.S. Provisional Patent ApplicationNo. 60/897,842, and U.S. patent application Ser. No. 12/569,733, nowU.S. Pat. No. 8,004,115, all of which are incorporated herein byreference.

The circuits are described below in relationship to an automatictransfer switch (“ATS”) that is connected to two separate power sources,A & B. It should be noted that the example ATS is for single phasepower, however polyphase ATS units can be constructed using the samecircuits, which would essentially be multiple single phase ATS unitsacting in parallel. The only change needed is to synchronize certain ofthe control circuits so that they act together across the multiple ATSunits to handle switching and return from the A polyphase source to theB polyphase source and back. The only change is to specify under whatconditions to switch power sources. For example, given three phase powerwith X,Y & Z hot leads, a fault on any of three might be consideredreason to switch to the B polyphase source. To return to the A polyphasesource, all three polyphase leads may have to be present and ofsufficient quality to enable the return to the A source.

In addition to the exemplary aspects and embodiments described above,further aspects and embodiments will become apparent by reference to thedrawings and by study of the following description.

BRIEF DESCRIPTION OF FIGURES

For a more complete understanding of the present invention and furtheradvantages thereof, reference is now made to the following detaileddescription taken in conjunction with the drawings in which:

FIG. 1 is a basic block diagram showing an overview of the Electricaland Electronic Subsections in accordance with the present invention;

FIG. 2A is a detailed block diagram of the Input Disconnect Switch andSync detector in accordance with the present invention;

FIG. 2B is a schematic of one side of the Input Disconnect Switch andSync Detector in accordance with the present invention;

FIG. 3A is a detailed block diagram describing the various functions ofthe components of the Input Selector (Gate Keeper) sub section inaccordance with the present invention;

FIG. 3B is a schematic of the Input Selection and Power SwitchingSection (Gate Keeper) in accordance with the present invention;

FIG. 4 is a Current Sense block diagram providing an overview of thecurrent sensing apparatus associated with detecting the output currentof the ATS in accordance with the present invention;

FIG. 5 is an Indicators and Communication block diagram providing anoverview of the communication apparatus and indicators used in the ATSin accordance with the present invention;

FIG. 6 is a Power Supply block diagram providing an overview of thevarious elements of the Power Supply system used to power the ATS andthe Remote Communications sections in accordance with the presentinvention;

FIGS. 7A-7F show timing diagrams providing an overview of the generictiming and sequencing of events in accordance with the presentinvention;

FIG. 8 shows a 30 amp corded Automatic Transfer Switch in accordancewith the present invention, shown in perspective and left end views;

FIG. 9 shows a 30 amp dual IEC type C19 Output, Corded Input ATS inaccordance with the present invention;

FIG. 10 shows a 20 amp dual IEC type C20 Input, Single IEC type C19 OutATS in accordance with the present invention;

FIG. 11 shows a circuit and method for detecting zero crossings inaccordance with the present invention;

FIG. 12 shows how the synch detector circuit extracts the AC inputvoltage valve in accordance with the present invention;

FIG. 13 shows a cross-section end view of the case of an ATS inaccordance with the present invention;

FIG. 14 shows components of a relay contact authentication detectionmodule in accordance with the present invention;

FIGS. 15A-C show block diagrams of an ATS including relay operationauthentication functionality in accordance with the present invention;

FIGS. 16A-16H show a circuit for implementing an inrush limitingfunction in accordance with the present invention;

FIG. 17 shows a high definition waveform sensor circuit in accordancewith the present invention;

FIGS. 18-20 show a variety of instantiations of an ATS in accordancewith the present invention;

FIG. 21 shows a number of options for utilizing an ATS as describedherein to increase the uptime and maintainability of an example SBCcontrol module; and

FIG. 22 shows a number of housing or case configurations in accordancewith the present invention.

DETAILED DESCRIPTION

An automatic transfer switch system is described below that has a numberof advantageous characteristics relating to data conductivity, compactsize, avoiding use of valuable rack space, primary power sourceselection, remote monitoring and reporting, maximum current control andthe like. Specific examples embodying these advantageous characteristicsare described below. However, it should be understood that alternativeimplementations are possible in accordance with the claimed invention.Accordingly, the following description should be understood as exemplaryand not by way of limitation.

The primary function of the ATS is accomplished by transferringelectrical power from one source to the other via a set of mechanicalrelays. In addition, the closure of these mechanical relays can beaugmented by the use of modern semiconductor switches, e.g., InsulatedGate Bipolar Transistors, (herein after referred to as IGBT) but thesedevices could be other semiconducting switches of sufficient Voltage andCurrent handling capabilities in the categories of TRIACS, SCRs, BipolarTransistors, Field Effect Transistors, or combinations of each. Thesecan be configured in a variety of ways, each with advantages anddisadvantages. A preferred instantiation as applied to this ATS isutilizing IGBTs. They are selected due to ease of turning them on andoff, robust construction, and resistance to false conduction.

The timing and execution of desired functions is accomplished utilizinga digital control circuit comprised of a peripheral interfacecontroller, or PIC. This device is a member of the “programmablefunction” devices and allows for a set of code to be recorded in thedevice that directs the actions of the overall digital control system.The PIC has sufficient computational capacity to perform certainmathematical computations to allow for precision calculation ofvoltages, current, time and other precision parameters necessary forvery precise control of the timing of the relays and solid-stateswitches.

The ATS also includes advanced communication capabilities via aconnection to remote EDP equipment for the purpose of reporting status,electrical characteristics of the attached electrical “mains,” and avariety of other information contents that could be useful in themaintenance of power systems attached to the ATS, either as source poweror as attached equipment (herein after referred to as the “load”). Thiscommunication portal on the ATS utilizes as a primary means ofcommunicating, the internationally accepted schema called UniversalSerial Bus (USB), and as a secondary communication protocol of PICKITprogramming transport. This secondary communication is included to allowfield upgrades to be made without requiring the ATS device to be openedup for access to traditional programming ports. A third communicationsmeans is also provided that allows simple Digital Serial Data to betransmitted and received by the ATS via un-encoded 5 Volt logic levels.This third communications means is provided to allow interfacing withlong-line communications means. The USB transport and protocols are notespecially well suited to transmitting and receiving data over distancesgreater than 10 to 30 meters. For applications requiring communicationin harsh environments over long distances, an interface is necessary toconvert the signals to various other standards. The availability of theraw “serial data” through the communication port enables the directattachment of alternate transport standards interfaces simply andeconomically.

Description of Circuit Operation.

FIG. 8 shows perspective and rear views of one instantiation of the ATS100. As shown, two power cords 106 enter the ATS (A power and B powerinputs) and one cord 109 exits the ATS (power out to the load). It alsoshows that the ATS has indicators 107 located beneath a clear crenelatedplastic lens 108 that also acts as the air inlets. Shown also is theaforementioned communication portal 103 and a small push-button 104 usedfor inputting some local control commands directly to the ATS.

The ATS 100 has a pair of small fans internal to the assembly thatprovide cooling to the various components inside as necessary. Thesefans are operated only as needed and only at what speed is necessary tomaintain acceptable operating temperatures. Two fans are included forredundancy, and the controller inside the ATS 100 can report via thecommunications port to remote monitoring equipment any detected faults,including the performance characteristics of either of the fans.Temperature at the air inlet of the unit as well as the air outlet isalso reported to the remote monitoring equipment.

Referring to FIG. 7, The Overview of Basic Switching Concepts, a basicunderstanding of the operation of the ATS can be gained.

FIG. 7A shows the off state of the ATS when no power is applied.Switches 2, 3, 91 and 92 are all open.

FIG. 7B shows the state when power is applied to the A input. The unitpowers up and the controller turns on the A input switch 2 and it alsocloses the Input Selection Switch 4 (herein after referred to as the GK,short for Gate Keeper) and is allowed to pass to the output through theGKA switch 91. Power can now flow from the A input to the output.

FIG. 7C shows the state when power is applied to the B input. The unitpowers up and the controller turns on the B input switch 3 and it alsocloses the Input Selection Switch 4 and is allowed to pass to the outputthrough the GKB switch 92. Power can now flow from the A input to theoutput. When power is applied to both inputs, as will be the normalcondition, then both of the Input Selection Switches will close anddeliver power to the GK 4 where the controller will direct either theGKA switch 91 or the GKB switch 92 to gate power to the output. Nevershould both GKA 91 and GKB 92 ever be closed at the same time. This willresult in shorting the two inputs together.

FIG. 7D shows the condition of having both GKA 91 and GKB 92 on at thesame time. A fuse located on one side of the A input 12 is shown “blown”or open, in this case. Since the GK has shorted both leads of A input toB input, then the opposing side must also be protected. The B input alsohas a fuse 13 on one of its inputs, but it is in the opposite lead path.It is also shown “blown,” or open. These two fuses 12, 13 not onlyprotect the load from exposing the circuit to a dangerous condition, butthey also prevent a serious overload of the input power sources in theunlikely event of a catastrophic internal failure of the ATS. Using thistechnique, two fuses can protect all 6 leads, two on the A input, two onthe B input and two on the Output, with any overload condition in anycombination.

FIG. 7E shows the introduction of the Solid State Switching elements 93,94. Mechanical relays all require some finite amount of time to operateafter the signal is applied to the coil, either to close or to open thecontacts. Solid State Switching devices generally have a very short timeto operate, on the order of microseconds. However, they do exhibit avoltage drop across the junction when conducting (closed) and thisvoltage drop represents loss of power in the circuit. For example, anIGBT based semiconductor AC switch (such as applied in thisinstantiation) exhibits a voltage drop of about 3 volts at 30 Amps ofconducted power. That relates to 90 Watts of loss. The equivalentmechanical relay will exhibit a loss of about 1 Watt at the same appliedcurrent. Thus, a mechanical relay augmented with a solid state relay isan ideal combination for maximizing efficiency as well as operationspeed. When desired to conduct, an augmented relay configuration asshown in FIG. 7E, the conduction of electrical current will commencewithin about 10 microseconds of the command to conduct. This allowsprecise timing of the connection to the power source. However, thedisconnect time is still subject to the response time of the mechanicalrelay since the contacts of the mechanical relay are in parallelconnection to the SSR element. Even though the SSR element maydisconnect, the mechanical contacts will remain closed for a short timeprior to releasing. This delay is of little consequence when switchingfrom one power source to the other when power is available on both, suchas is the case when the ATS is returning to the preferred side after thepower has been restored on that preferred side. Precise timing of thedisconnect can be accomplished in this case because the mechanical relaycan be commanded to release prior to the desired time of the actualdisconnection, while the SSR is still conducting. Then, at the desiredtime of disconnection, the SSR can be commanded to release. Thus, formost conditions, precise timing can be achieved, with little power lossin this configuration. The use of the IGBT and bridge AC switch has theadvantage of being able to turn on and off in very short time periods.It is difficult to turn off a Triac, or an SCR based switch, as thosedevices want to stay on until current stops conducting, thus they stayon until the AC current passes through the zero crossing as the sinewave changes polarity. In the example shown in FIG. 7E, The SSR on sideA 93 is shown in the on condition, and conducting power to the Outputwhile the mechanical relay contacts of GKA 91 are moving to try toclose. Any variation in timing that might be imposed by the mechanicaleffects of the motion of the relay contacts are masked by the SSRconducting. Albeit the associated power loss intrinsic to the SSRdelivering the current is present during this time, it is of only a veryshort duration, about 10 milliseconds, before the mechanical relaycontacts close, thus reducing the power loss to a minimum. The SSR canremain on but it will have no effect.

FIG. 7F shows the final configuration with power being conducted throughthe GKA relay 91 to the output and bypassing the SSR 93.

Sub-Circuit Detailed Descriptions

FIG. 1 shows the general configuration of all of the sub-circuits andhelps identify their function in the overall operation of the ATS. Notethat both the A side AC power connection and the B side AC powerconnections pass through a “N” Side Disconnect and Sync Generationsub-circuits 2,3. When AC voltage is not present on the input to one orboth of these circuits 2,3 the internal mechanical relay inside of thiscircuit remains in the “open” state, thus no power is passed through tothe Gate Keeper 4. These “N” Side Disconnect and Sync Generationsub-circuits 2, 3 provide several functions to the operation of the ATS.

Disconnection from the GK 4 when power is not present on the inputprovides safety disconnection from the source and provides requireddisconnection isolation voltage capacity required by various safetyagencies such as Underwriters Laboratory (UL). The mechanical gap on therelay contacts prevent voltages as high as 3000 Volts from passingthrough. Commands from the Digital Control Electronics 1 can command the“N” Side Disconnect and Sync Generation sub-circuits 2, 3 to engage ordis-engage, as timing needs are satisfied. The “N” Side Disconnect andSync Generation sub-circuits 2, 3 also have a circuit in them thatdetects the AC voltage near the point where it crosses zero whenchanging from one polarity to the other. This signal generation allows apulse to be generated that is symmetrical about the zero crossing to beformed and sent to the Digital Control Electronics 4 for use inproviding information needed to electronically synchronize and controlthe various actions of the ATS.

FIG. 11 shows the simplified means that this is accomplished in the “N”Side Disconnect and Sync Generation sub-circuit. The circuit 200 iscomprised of three main elements, the input bridge 202, comparator 203and isolation optical coupler 205. As AC voltage is applied to the input201 it becomes rectified in the bridge 202. The rectified voltage isscaled down to a useable voltage by resistor divider R1 and R2 and thatvoltage is applied to the input of the comparator 203. The other inputof the comparator 203 has a reference voltage applied to it formed bythe resistor divider R3 and R4 and is filtered by the capacitor C1. Whenthe applied rectified voltage from the AC bridge becomes greater thatthe reference voltage, the output of the comparator 203 switches “On,”in this case the output goes to 5 volts, or High. When the appliedrectified voltage from the AC bridge becomes less that the referencevoltage, the output of the comparator 203 switches “Off”, in this casethe output goes to 0 volts, or Low.

The synchograms 300 show the voltage—time waveforms typical of thiscircuit 200. The AC In 207 is rectified 208, and when the thresholds arecrossed, the output of the comparator produce pulses 209 at the pointwhere the original AC in 207 crosses at the zero crossing plus thethreshold of the comparator. These pulses are nearly symmetrical aboutthe actual zero crossing of the original AC In voltage.

The Sync pulse formed in “N” Side Disconnect and Sync Generationsub-circuits 2, 3 also carries information about the applied voltage tothat circuit in the form of the pulse width. As the voltage increasesthe pulse width becomes narrower and narrower. This allows detection ofthe applied voltage by the Digital Control Electronics on the samesignal path as the synchronization pulse.

FIG. 12 shows how the sync detector circuit also functions forextracting the AC Input Voltage value in the Digital Control ElectronicsSection. Assuming a high voltage of, for example, 240 VAC, isrepresented by the synchogram 300 at the AC In 207. The rectifiedVoltage 208 is then crossing the threshold and results in pulses 209formed that are narrow. But, if a lower voltage, say 120 VAC is appliedas shown in the second synchogram 301 the voltage threshold of therectified AC voltage 221 is crossed sooner and as a result theComparator Out 222 pulses become wider. The Digital Control Electronicscan compare the time of the rising edge to the falling edge of thesepulses and apply mathematical formulae to retrieve the exact voltagethat is represented by those pulse widths. Alternatively, the DigitalControl Electronics can hold a table of representative values that, whencompared to the detected pulse width times, can also result in veryaccurate representations of the applied voltages.

The output of the comparator circuit in the “N” Side Disconnect and SyncGeneration sub-circuits is passed through an optical isolation circuitto make sure that the Digital Control Electronics is electricallyisolated from any AC or DC Voltage applied to the inputs. This is asafety requirement and is enforced by various regulatory agencies suchas Underwriters Laboratory (UL).

FIG. 2B shows the schematic of the “N” Side Disconnect and SyncGeneration sub-circuits. The AC filter section 21 shows a simple Pifilter attaching the AC mains to the electronics of the “N” SideDisconnect and Sync Generation sub-circuit via a fuse F5 of 250 ma. Apair of inductor and a capacitor are used to prevent any high frequencynoise generated in the attached circuits 22 from entering the AC mainslines. This is done to prevent interference with other external electricand electronic devices. This is also necessary for various complianceagencies such as Federal Communication Commission, of FCC, as well asothers. After power is filtered, it is delivered to the SwitchmodeCurrent Limiter 22 where the AC high voltage is rectified in D2, D3 D8and D9 and delivered to the filter capacitor C2 via D4. D4 isolates therectified DC from the bridge from the filtered DC of C2. The un-filteredrectified DC is delivered to the comparator through the resistivedivider R6 and R5 for developing sync and voltage data as previouslydescribed. Rectified and filtered DC voltage at C2 is delivered to theSwitching chip Q9 via a filter inductor pair of L10, a ferrite bead forvery high frequencies, and L12, for medium frequency limiting. Theswitching chip Q9 turns on and off at about 80 Khz, and the duty cycledetermines how much current is present in L1. Since this is switchinginto L1 from a monopolar source, the flyback energy in L1 is containedby D10. The Switching chip chip Q9 is pre-programmed to adjust the dutycycle to maintain a constant current of 20 ma. This chip is originallydesigned for use in modern LED lighting, but is r purposed to simplifythe power supply design of this invention. The varying pulses in L1 aretranslated to a fairly constant current of 20 ma and then is allowed topass through the coils of the two relays 21 that switch on the main ACpower. The other side of the two relay coils 21 enter the On-Off Switch23 at the Drain of Q5. If Q5 is “On,” the current then passes to thesecondary filter capacitor C7 In the Sync Pulse Generator section 25. 20ma ov current is presented to the Cathode of ZD3, and when the voltagereaches 8.2 Volts, the Zener conducts to maintain about 8.2 Volts. Thisvoltage is presented to the input of the 5-volt regulator Q7. This is aprecision 5-volt linear regulator. As long as the total powerrequirements of the output of the regulator, and the attached circuitsdoes not exceed 20 mA, then ample overhead voltage will be present tomaintain precision 5-volt regulation. The design of the Sync PulseGenerator 25 Comparator circuit is such that there is very littlecurrent necessary to accomplish the detection function. Only about 2 mAis actually used in this part of the circuit. This leaves 18 maavailable. Some of the 18 mA available at the input to the 5 voltregulator Q7, is diverted to the opto-coupler U4 26 and through the 1Kresistor connected to the output of the comparator U7. If the U-7 is inworst case voltage detection mode, where the output is “on” (or low) allof the time, then all 8.2 Volts is dropping through the 1 K resistor,minus the 2 volt drop of the LED in the opto coupler U4. The resultantmaximum current is 6.2 mA. Thus, for all cases, the series switch moderegulation of a total of 20 mA, is adequate to drive all possiblecombination of circuit requirements.

This method was chosen to optimize the efficiency of operation of thecircuits. Very little power is wasted, and the total circuit powerefficiency is about 84%. The total quiescent power used to operate the“N” Side Disconnect and Sync Generation sub-circuit is about 0.65 Watt.Both the A and B sides add up to around 1.3 Watts. This is a very highefficiency for all of the functions achieved.

This scheme also makes the operation of these circuits functional fromabout 30 Volts of AC applied to the mains inputs all the way up to 300Volts. These circuits must function across the maximum range of AC inputvoltages to allow monitoring and functionality of the ATS regardless ofthe voltage applied.

A signal that comes from the Digital Control Electronics, “ForceDisconnect” 27 is presented in cases where the Controller wishes to shutoff an input. This is done during every transfer cycle to prevent anypossibility of carrying an arc between the contacts of the Gate Keeper(FIGS. 3, 39 and 40) that would cause a short between the A side and theB side Power Inputs.

The “Force Disconnect” 27 signal causes the LED in the opto-coupler Ulto turn on the phototransistor in Ul, which in turn shorts the Gate ofQ5 to the Source of Q5. This turns the Q5 Drain off and shuts off thecurrent path to the relays. About 2 ms. Later the relay contacts openand power is disconnected between the input and the output of theDisconnect relays 21.

When the “Force Disconnect” is removed from the opto coupler Ul, and thephototransistor turns off, then current from R1, 3.9 Meg ohm resistor isapplied to the gate of Q5, the voltage rises to about 10 volts veryquickly and the Drain of Q5 is connected to the Source and Q5 is turnedon. Current can now pass through the coils of the switching relays,sourced by the switch mode chip Q9, as described earlier. The relays 21are now energized and the contacts are closed about 7 to 10 ms later.

During the time that a “Force Disconnect” is present, there is no needfor sync pulses during the transfer process. Voltage and timing havealready been determined by the Digital Control Electronics. But a “ForceDisconnect” usually only lasts for 20 ms or so, just long enough tocomplete a transfer. During that 20 ms, power stored in C15 keeps thecomparator operational, and pulses can continue to be detected if thereever became a need to utilize the information. FIG. 3 shows the detailedblock diagram of the Input Selector, or Gate Keeper (GK). This is thecore of the ATS. This is where power from either the A side DisconnectSwitch, of the B side Disconnect Switch is directed to the Output andeventually to the “load”. Its operation is directed entirely by thecommands from the Digital Control Electronics. When no signals arepresent from the Digital Control Electronics all of the relays in theGK, and the Solid State Relays (SSRs) are in the open, non-conductingstate. This presents a “Fail Safe” condition.

In order for the Digital Control Electronics to direct power from the ASide Disconnect Switch output, it must first make sure that no controlsignal is being sent to the B side steering circuits. A special piece ofcode in the Digital Control Electronics makes this check every time aattempt to change the state of either input is made. It is critical thatthe A side and the B side are never connected to the output at the sametime, as this would result in a short circuit between the A side and theB side inputs and would cause a fuse to blow, and perhaps more damage. Asecond layer of protection is included with the implementation ofhardware interlock 49 that prevents two commands from conflicting. Forexample, if the Digital Control Electronics requests that the A relaycoil driver turns on by asserting the control line 42, that signal willalso be present at the input of the logic gate 46. Since the true stateof the A side request is inverted at the input to the logic gate 46, anysignals present at 41, the control line that would drive the B side, isblocked by the gate 46. Conversely, a signal from the Digital ControlElectronics requesting to turn on the B side Relay Coil Driver 41 thatis asserted will be present at the inverting input to the logic gate 43and in turn mask any signals coming from the A side Digital ControlElectronics command 42 to turn on the A side Relay Coil Driver. The sameconcepts apply to the IGBT drivers. These function similarly to theRelays, but with nearly instantaneous response times. The commands toturn on one side or the other will result in a masking signal sent tothe opposite side and prevent a dual turn on condition to exist. A“high” in the IGBT drive A side control input 47 will be presented as alow to the gate on the b side 45 and inhibit any signaling from theDigital Control Electronics from passing through the gate 45.Conversely, A “high” in the IGBT drive B side control input 48 will bepresented as a low to the gate on the b side 44 and inhibit anysignaling from the Digital Control Electronics from passing through thegate 44. 5 KV Optical Isolators are included between the Digital ControlElectronics and the IGBT Drivers. This is necessary since the IGBTdrivers operate at the AC Line voltage potential of their respective ACsources. The Relay Coil Drivers do not require isolation, the Coils ofthe relays 39, 40 are isolated from the AC Line voltage mechanically.

FIG. 3B shows the detailed Electronic Schematic of the Input Selector,or Gate Keeper (GK). When the Digital Control Electronics determinesthat the A side AC power should be connected to the Output, it simplyasserts both the Gate Keeper o A (GK to A) signal and IGBT Drive A. The5 volts logic control signal presented at GK to A will turn on the FETQ11. It's Source is connected to ground, so the Drain goes to ground,thus supplying current to the coils of the A side Gate Keeper relays, RY3 and RY 7 These relays acquire coil current from the +12 Volt powersupply. Magnetic field current starts to build in the coils and therelay is starts to energize. Generally speaking these relays require 7to 10 ms to operate. The bigger the relay, the slower the operation,generally. During this time the second half of the operation has begun.The Digital Control Electronics has also issued a assert command to theIGBT Drive A input. This High level (5 Volts) signal sends current tothe LEDs of U 13 and U 15, 5 KV Isolation opto-couplers, via resistors27 and 28. This current is dependent on Q14 a PNP bipolar transistorbeing turned on also. The turn on of Q4 is generally present due to thebase pull down resistor R31. If, for some reason, the IGBT Drive B washigh (asserted for some reason), the base of Q 14 would also be high,and no current would be able to go through the collector of Q14, thusdisabling the IGBT Drive A command. The transistor Q14 is essentiallythe logic gate discussed prior with FIG. 3A, Logic Gate 44. This is thesecond layer fail-safe discussed earlier. However, assuming that theIGBT Drive B is not asserted, and that the IGBT Drive A is asserted, andthat current is now flowing in U 15 and U 13, the other side of thoseopto-couplers will now be also conducting.

To understand how the IGBT drivers turn on the IGBT, it must be assumedthat AC power has been present coming from the A Side Disconnect Switchfor at least a little while. That AC Voltage that has been present hasbeen conducting through Diodes 13 and 32, and R 41 and R3, chargingCapacitors 26 and 32, each to 20 Volts. When these capacitors reach 20Volts, the current is diverted through Zener Diodes ZD 5 and ZD 1, andthe voltage remains at 20 Volts. The capacitors are 4.7 micro-Faradseach. The amount of charge they hold is important later on in thediscussion.

When the optical coupler photo transistor in U13 turns on, 20 volts fromC26 will be conducted through R9 and on to the base of Q13 and resistor2. Capacitor 33 presents a very short impedance to this turn on andfilter out transient noise. Otherwise, Capacitor 33 has no effect. Whenthe voltage is applied to the base of Q13, the voltage rises very fast,limited essentially by the charge rate of C33. As the Base of Q 13rises, the transistor releases its current path from the Emitter to theCollector, essentially shutting off this transistor. The rising voltageat the base of Q 13 now is passed to the base of the IGBT Q2 via thediode 21. These rising voltages are now limited by the base capacitanceof the IGBT Q2 and the current limiting of the Opto coupler and R33.Since the opto coupler is around 200 ohms at this time, the rise time isrelatively fast, on the order of 150 microseconds. The IGBT Q2 is nowconducting. Any AC Voltage that appears across the contacts of the RY7at this time is shunted through the Diode Bridge BR2 and through theIGBT Q2 Collector-Emitter. Effectively, the AC inputs to the bridge BR3are shorted. This whole process has taken about 200 micro-seconds.Meanwhile, the Relay 7 is just starting to energize. It will be another7 to 10 ms before it actually has the contacts meet one another. The ACinput to this side of the Load is now connected.

The same process is occurring on the other half of the A side IGBTdrive, the side driven by U15. Ultimately, IGBT Q3 will be turned on,shunting Bridge 3 and delivering AC power to the other side of the Aside path between the A side Disconnect Switch to the Output and to theload.

After a period of around 100 ms, it is assumed that the relays haveclosed and that all of the current is bypassing the IGBTs. The DigitalControl Electronics will de-assert the IGBT Drive A and the IGBT Drive Bcontrol signals. If, for some reason the Digital Control Electronics didnot release the drive signals, a designed in feature of the IGBT Driversthemselves will release the drive signal from the IGBT gates anddisconnect the devices. This is accomplished by the decay of the storedcharge in the aforementioned C26 and C32. The current path from the C26and C32, through the opto couplers and through the 68 K base resistorsfor Q 13 and Q 21 will eventually discharge the C26 and C32 to the pointwhere the IGBTs do not have sufficient voltage on the Gates of thesedevices to sustain current flow in the Collector to Emitters of Q 2 andQ3. Even though some current is being supplied to the C 26 and C32 fromthe D13 and D32, the resistive divider of 560K and 68 K, through a halfwave rectifier, will not provide sufficient voltage at the base of theIGBTs to sustain current. At maximum input voltage to the ATS of 277volts AC, only about 6 volts will be present at the gate of the IGBT andthe device will turn off. Careful selection of components has enabledthis feature without the addition of any additional circuitry.

When the Digital Control Electronics determines it is time to shut off aparticular side of the GK, there are two possibilities. One is for animmediate shut off, implying it is being turned off as fast as possibledue to a loss of voltage on this path. This would be the case when, forexample, this is the A side, the A side is the preferred, and the loadhas been connected to the A side for some time. This is a normal state.

When the A input AC voltage fails below an acceptable level, the controllogic can determine that the A input power is failing and an outage (vs.a power quality disturbance for example) is in progress. It is nownecessary to transfer to the alternate power source (the B side in thisexample) as fast as possible. The first action to consider after theDigital Control Electronics has determined that the failure is valid byobserving the a Sync pulse occurred at a time it shouldn't have, or thesync pulse was longer than it should be, the Digital Control Electronicswill immediately start the disconnect process. It is paramount that thefailed AC power input be totally disconnected from the output prior toconnecting the alternate side power source to the Load. Otherwise,current would be transferred from the Alternate power Source to thePrimary power source, which could be at a very low impedance (forexample, the whole AC grid). So, knowing that it has taken a couple ofmilliseconds to verify that a failure has happened, another twomilliseconds (plus a little buffer insurance of 1 millisecond) isdesirable to ensure that the Input Relays and the Gatekeeper Relays havehad sufficient time to mechanically open. As mentioned before, this timeis on the order of 2 milliseconds average. Thus, the command to “ForceDisconnect” the primary side (A in this example) is immediately issuedalong with the GK to A control lead being de-asserted. This starts theprocess of disconnecting from the A side. It is assumed that the IGBTDrive for the A side has long since been removed, preferably about 200ms after it was asserted long ago when power was initially transferredto the Primary side.

The Digital Control Electronics must now wait patiently for at least twomilliseconds. The ATS Digital Control Electronics actually waits 3.5 ms,with the relays we are currently using, but this value is programmableinto the Digital Control Electronics and may change depending on therelays sourced for use in these ATS units. But it does wait until it issure that enough time has passed that the mechanical relays have openedthe path from the previously connected Power source and the output. Atthis point, The Digital Control Electronics can assert the IGBT Drive Band the GK to B signals and connect the load to the alternate powersource as described in the connect sequence above.

When the IGBT drive is off, and the opto-couplers are not turned on,there is no current source to keep C33 (C47) charged and they decay involtage down from wherever they were until these capacitors are fullydischarged via resistors R2 and R4. At this point, the bases of Q 13 andQ21 are at the collector potential. Q13 and Q21 are Darlington coupledtransistors and have gain characteristics in excess of 20,000. Anyattempt to raise the voltage on the emitters of these transistors Q13and Q21, will result in immediate conduction to the collector potential.In other words, the Gates of the IGBTs Q 2 and Q3 are shorted to theirEmitters. This is necessary. Because the Collectors are connectedindirectly to the output of the ATS via the Bridges BR2 and BR3, whenthe IGBTs on the Alternate side do come on, and deliver AC to the Loadfrom that side, they will turn on very fast. The resultant very highrate of voltage change at the output will appear at the Collectors ofthe now off IGBTs Q2 and Q3. Without the very low impedance clamp on theGates of the IGBTs Q2 and Q2, the high rate of rise at the Collectorswill try to turn on the IGBTs through the capacitive coupling internalto the devices. The higher the rate of rise of the voltage, the moresusceptible the IGBTs are to false turn on. Thus, the ever-present clampacross the Gate to Emitters of the IGBTs when they are off. This uniqueIGBT drive scheme is both simple and robust. It requires no externalpower to operate. Switching on the alternate side from IGBT Drive B andGK to B are mirrored in function to the A side.

FIG. 4 shows how the ATS monitors current and retrieves data necessaryfor synchronization of zero crossing using the output current. As anATS, the decision to transfer a load from one active AC power source toanother active AC power source requires additional considerations otherthan performing the transfer as quickly as possible. Since both ACsources are present, there may be additional considerations to make whendeciding when to disconnect from the active source delivering power tothe load, and then connecting it to the active AC source that isconsidered the Primary source. This event occurs every time there is apower outage on the primary source, the ATS transfers to the alternatesource, and then eventually the Primary AC power source is restored. ATthis time, the transfer the ATS must make is from one good source toanother good source.

It is necessary to make the opening of the relay occur at or near thezero crossing of current when disconnecting a load from an active ACsource. This helps fervent contact arcing and extends the life of therelay contacts. In the ATS described here, the Disconnect Relays in theDisconnect Switch and Sync Section do not have solid state bypasscircuits to unload the current from the relay contacts during adisconnect. Thus, the disconnection must be synchronized with the zerocrossing of the current in the circuit.

The ATS described herein can deliver power to a variety of load types.One such load type is what is referred to as a reactive load, oftenfound where the load has capacitance, inductance, or a combination ofboth. When there is capacitance or inductance in the circuit, thevoltage and current waveforms are not synchronous. The power flow hastwo components—one component flows from source to load and can performwork at the load and the other component known as the “reactive power”,is due to the delay between voltage and current, referred to as phaseangle, and does not do useful work at the load. It can be thought of ascurrent that is arriving at the wrong time (too late or too early). Thisphase difference between the actual voltage zero crossing and the zerocrossing of the current requires that, since the relay contacts can bedamaged by current, not volts, it becomes necessary to cause the relaycontacts to open at the time that the current is passing through thezero. Since this can be different timing from the zero-crossing detectedin the Disconnect Switch and Sync Section, an alternate method ofdetermining the timing of the relay opening, and it must be based on thecurrent flow instead of the voltage present.

When power is present on both sources, and a transfer is imminent, theDigital Control Electronics must measure the output current, and if itis significant, use this to determine when to open the various relays inthe path of the current flow. In the ATS described here the DigitalControl Electronics has tables loaded into its memory at the time ofmanufacture that contain the measured time between the command torelease a given relay, and when it successfully opens the contacts.Generally, this time is about 2 milliseconds, but it can varysignificantly due to manufacturing variables. Thus, the Digital ControlElectronics keeps track of the delay times for each of the relays in theATS and can use that information to calculate the exact disconnect timewhen preparing to disconnect the load from an active AC source.

The Digital Control Electronics also has determined the time fromone-half cycle to the next by measuring the rising edge to the risingedge of the sync pulses generated in the Disconnect Switch and SyncSection. By using this information, the Digital Control Electronics cannow subtract the known delay of a given relay from the time between halfcycles and arrive at a number that is predictive of when the relaycontacts will start to open, relative to a zero crossing of current. TheDigital Control Electronics will prepare to make the relay opening, thenat the next zero crossing of the current will then delay the amount oftime calculated by subtracting the relay opening time from the halfcycle to half cycle time, then the Digital Control Electronics issuesthe disconnect command.

In this manner, the ATS described here can disconnect a load very closeto the actual zero crossing of the current by performing thesepredictive calculations. This minimizes the degradation of theelectrical contacts within the relays. In addition, conditions couldexist that prevent a relay contact from releasing when the command fromthe Digital Control Electronics commands it to disconnect. The mostcommon cause of this is a welded contact that is the result of someexcessive current during the prior transfer. Other conditions couldinclude mechanical wear or degradation of materials due to time, heat orother causes. In any of the cases where a contact has not operated inthe manner desired by the Digital Control Electronics, a method isdescribed here that allows the Digital Control Electronics to detectthat fault condition. If the fault condition is detected before thecommands are issued for any additional relay or SSR action, then ashorting of the A side power source to the B side power source can beavoided. In much large Automatic Transfer Switch applications,traditional ATS designs, this is accomplished by mechanically linkingthe power contacts of the relay to an auxiliary set of contacts that canbe monitored by the Digital Control Electronics for this authenticationprocess. In the case of the MINI ATS application described here thephysical size is of significant concern. A novel means of detecting theoperation of the relay is described here, referred to as the RelayOperation Authentication Detector, that allows this authentication,while maintaining a small form factor. In addition, this detection meansis directly involving the active electrical conductive portion of therelay that actually passes the power through the relay. By detecting onthat specific electrical conductor, there is positive confirmation ofthe state of that contact, either connected to the power source or notconnected. When the Digital Control Electronics commands either theclosure of the desired relay or opening of the desired relay, thisauthentication feature allows the Digital Control Electronics toimmediately check the results of that action request and verify it hascompleted before moving on to performing any other actions. In the eventof detecting a failure to complete the command by the relay in question,the Digital Control Electronics can then undergo a process to halt anyadditional actions, report this fault event to the monitoringcontroller, and it can perform multiple attempts to operate the relayand possibly self-repair the electrical fault by breaking loose thepotentially welded contact. In that event, the Digital ControlElectronics can then elect to return the entire MINI ATS to operation orplace it in a safe state such as totally shut down. The determination ofwhat to do with the fault condition is fully programmable and can bespecific to various applications. This flexibility offered byimplementing the authentication is unique in Automatic TransferSwitches.

In addition, the authentication circuits allow the Digital ControlElectronics to operate in a mode where the next step is not determinedby time as described earlier, but by what state the various componentsare physically, or electrically in. For example, when the command todisconnect the relay from one source is issued, instead of calculationwhen it should have disconnected, to allow proceeding, the DigitalControl Electronics simply waits for the authentication signals from theaffected relays to indicate a successful completion of the action. TheDigital Control Electronics merely has to put a timed limit on that sodetection of a fault can be determined. But being a state-controlledprocess means that the next action that is dependent on the upcomingchange of state is timed to the optimum time when that next action cancommence.

FIG. 4 shows the basic electrical and electronic components of theCurrent sensing section of the ATS. The primary sensing element is aHall Effect sensor 51 adjacent to the Hot Out Lead that is attached tothe output of the ATS. The magnetic fields generated by the passingcurrent 57 is detected in the Hall effect sensor 51 and amplified. Zerorestoration 52 of the sensed signal is necessary to stabilize theconversion from AC measurement to DC in the Precision Rectifier 52.After the Current waveform has been rectified, it is still returning tozero every half cycle. At the moment it returns to zero, the ZeroCrossing Detector 55 output asserts. This signal is sent to the DigitalControl Electronics for use in calculating timing. In addition, therectified current output of the Precision Rectifier 52 is also sent toan integrator that consists of an array of capacitors and resistors thatsmooth out the sensed current and convert it to a smooth DC level. ThatDC level then is sent to the Digital Control Electronics via a bufferamplifier and enters the Digital Control Electronics through anintegrated Analog to Digital Converter for digital processing andreporting of the current levels to the communication port, andeventually to the remote monitoring equipment.

The Digital Control Electronics also uses the integrated DC levels todetermine if the ATS should turn on the light that warns of “maximumload acceptable.” A feature of the ATS described here is its ability toset a warning light when the load is above a pre-programmed level.

Another action that the Digital Control Electronics can perform usingthe integrated DC level is to shut off the output in the event of anoverload. If the current exceeds a pre-programmed level, the ATS cande-energize the Gate Keeper relay very quickly to protect the AC powercircuit. The Digital Control Electronics can then turn on anotherwarning light to indicate that an overload has occurred, and it can sendstatus data through the communication port to the remote monitoringequipment.

Another feature of the ATS described here is its ability to set awarning light when the load exceeds a pre-programmed level and turn offpower to that load coincidentally.

A reset button (FIGS. 8, 9, 10, item 104) is provided as a means for theoperator to reset a Load-Fault condition once the fault has beenremoved.

Unique filtering at the hardware level in the integrator 54 and softwarecomputations by the Digital Control Electronics allow a preciseimitation of any fuse curve desired, or any circuit breaker desired.

The output current sense discriminated by the Digital ControlElectronics can also be used to predictively operate the cooling fans.Instead of waiting until the interior of the ATS has heated up due toheavy loading, and then turning on the fans, the Digital ControlElectronics can predict the internal heating due to detected load in thecurrent sensor 11. Thus, the fans come on before individual componentsbecome hot. This feature can be useful in improving the reliability ofthe ATS.

The ATS can be predictive about internal heating and start the fan(s)proactively to reduce materials fatigue and improve reliability.

FIG. 5 shows the overview of the Indicators 9 in the ATS, and theCommunication port 10. The Indicators are generic LEDs of variouscolors. Utilizing state-of-the-art components, bright and efficient LEDsprovide excellent indications of the various statuses of the ATSdescribed here. The unique crenelated lens assembly allows effectiveairflow as well as an excellent range of angles of visibility of theLEDs.

In addition, a current limiter 60 is in the path of the electricalsupply for all of the LEDs. This prevents overloading of the powersupply in the event that 3 or more LEDs are illuminated simultaneously.

The Communication portal 10 provides a specialized communication setbetween the Digital Control Electronics and the remote monitoring andcontrol electronics.

Three functions are provided by this port, but others could also beimplemented.

-   i. USB communication with the remote monitoring and control    electronics.-   ii. Connection between the Peripheral Interface Controller (PIC) (a    type of MCU) internal to the ATS described here, and an external    programming tool. This allows updating the software (firmware) of    the PIC without having to open the case up. There may be customers    that have ATSs as described here that require special functions. Due    to the unique design of this ATS, these client needs may be met by    supplying specialized operating code to the Digital Control    Electronics of this ATS.-   iii. Connection between the Digital Control Electronics and external    communication interface converters to allow long line communications    to remote monitoring and control electronics. USB has short length    limitations and as such may not be applicable to all communications    requirements.

The Digital Control Electronics can send data via USB to the remotemonitoring and control electronics via the USB 2.0 interface converter71 through the panel accessed USB type C connector 72. A USB type Cconnector is selected for its unique pairing of pins that generallyallow the connector to be mated in either polarity. The pins from oneside of the connector are mirrored on the other side of the connector sothat regardless of which way the mating connector is inserted, thecommunication and voltages sent through the connector system will bepreserved. The ATS described here leverages this bi-polar characteristicfor an added feature. By flipping the connector, that flip can bedetected and send an alert signal 76 to the Digital Control Electronicsvia a Polarity Detect circuit 70. The Polarity Detect circuit operatesby detecting if a ground pin is present on one of the pins. Thecomplement pin (in a reversed condition of mating the connectors) isconnected, instead, to the +5 volts pin of the connector. In thismanner, the orientation of the connector can be determined by theDigital Control Electronics. This is useful by allowing the DigitalControl Electronics to determine if it should be communicating via USB,or if it should be preparing to accept data from a remote programmingtool. This feature also can be used to alert the operator that theconnector is flipped. This can be used to help improve the security ofthe data contained in the Digital Control Electronics. By flipping theconnector one way, a physical barrier to writing data into the DigitalControl Electronics. However, flipping the connector the other wayallows data to be written to the Digital Control Electronics, whilesimultaneously the Digital Control Electronics can provide distinctiveillumination to the LEDs that alert the operator to this writevulnerability.

Thus, the unique wiring of the USB type C connector allows the ATSdescribed here to communicate with multiple types of externalelectronics and improve the security of the data stored in the ATS.

FIG. 6 shows the overview of the power supply system in the ATSdescribed here. Since it is unknown at any time if power will be presenton the A input, the B input or both, a power supply system is includedthat is both 5 KV isolated from the Digital Control Electronics, but itis available from both the A and B inputs. A 12-volt DC supply isattached to the output of the A Side Disconnect and Sync AC Power out.Also a 12-volt DC supply is attached to the output of the B SideDisconnect and Sync AC Power out. Each of these power supplies areconnected to a common +12 bus via isolation diodes 86 that are containedwithin the power supply modules. These diodes provide the capability ofeither power supply to operate if one or the other fails. This is aredundant power supply system and is an added feature of the ATSdescribed here.

The 12-volt bus is distributed to the various electronics on DigitalControl Electronics 1 and the A or B Side Selector 4 electronics wherethe 12 Volts DC is reduced, if needed, to 5 Volts and 3.3 Volts asnecessary with local regulator chips. The inputs to the 12 Volt powersupplies are protected by fuses 89, 90 for safety reasons.

In addition to the local ATS power supply, an auxiliary power supply 81to deliver power to the USB port 91 is provided. This is a 5 Volt 2 ampsupply and again is Isolation Rated to supply power to the USB clientdevices in accordance with regulatory agency requirements such as theUnderwriters Laboratory (UL) and other similar regulatory bodies.

The input to the USB power supply 81 is supplied via a selector relay88. Each of the inputs to the selector relays have a single fuse in line84,85 to protect the 5 Volt power supply 81 and to prevent thepossibility of a through relay short circuit path between the A side andthe B side, in the event of a catastrophic failure of the selector 81.

FIGS. 8, 9 and 10 show various instantiations of the ATS 100.

FIG. 8 shows a variant that has flexible cords entering 106 and exiting109 the ATS described here 100. This is a 30 amp, or 32 Amp model, butother current handling capacity cordage can easily be applied. Variousamperage capacity models differ only in the cords, the connectors on theends of the cords, the internal main fuse ratings, and thepre-programmed information contained in the memory of the DigitalControl Electronics. Voltage range selection is automatic in the mainunit 100 but will be largely determined by the plug type installed.

The output cord 109 of the ATS described here 100 exits the end cap 101through a strain relief bushing 102 that is selectable for the cablesize without varying the size of the hole in the end cap. This reducesmanufacturing costs.

The output end cap 101 also has the portal for communications 103described in FIG. 5, element 72. The end cap 101 also contains the pushbutton 104 for resetting the ATS electronic circuit breaker or selectingthe preferred input.

FIG. 9 shows a variant that has flexible cords entering 106 and a pairof IEC type C19 receptacles mounted in the end cap 101 of the ATSdescribed here 100. This is a 30 amp, or 32 Amp model. Amperage capacitymodels differ only in the specifications related to the country of usageassigned, the internal main fuse ratings, and the pre-programmedinformation contained in the memory of the Digital Control Electronics.Voltage range selection is automatic in the main unit 100.

The dual IEC type C19 connectors of the ATS described here 100 aredirectly mounted in the end cap 101.

The output end cap 101 also has the portal for communications 103described in FIG. 5-72. The end cap 101 also contains the push button104 for resetting the ATS electronic circuit breaker or selecting thepreferred input.

FIG. 10 shows a variant that and a pair of IEC type C20 chassis mountplugs 121 on the entry to the ATS described here 100. A single IEC typeC19 receptacle 120 is mounted in the end cap 101 of the ATS describedhere 100. This is a 16-amp model. Voltage range selection is automaticin the main unit 100.

The output end cap 101 also has the portal for communications 103described in FIG. 5, element 72. The end cap 101 also contains the pushbutton 104 for resetting the ATS electronic circuit breaker or selectingthe preferred input.

FIG. 13 shows a cross section end view of the extruded case 201 of theATS. The case has numerous features including:

-   i. Extruded aluminum for strength and durability-   ii. All metal construction minimizes electrical and magnetic    interference problems-   iii. Slots on each side of the case with ample surface area for    dissipation of heat-   iv. Slots on each side for mounting.

The slots on the sides are configured at “T” slots, meaning that theslot has a small cavity behind the slot that facilitates ease ofmounting with a variety of hardware. The size and shape of these “T”sots is optimized for use with off-the-shelf mounting hardware.Generally speaking, “T” slots are commonplace, but in this instantiationthe slots have additional features that make them unique.

The slots are extruded for the whole length of the case. This allowsmounting fasteners to be inserted from either end and positionedlaterally along the length of the ATS to facilitate locating adjoiningholes in mating apparatus such as computer racks, clamp assemblies,flexible hinges, and so on. In addition, the spacing of the slots withrespect to each other is such that a standard off-the-shelf DIN rail canbe inserted directly.

In addition, each slot also has a rib along the centerline 212 that actsto engage with the slot in standard round head and flat head screws.

In addition, the slots have relief grooves 213 in the sides of the slotsthat facilitate a standard off-the-shelf flat washer when fastenerhardware has variable size head flange widths.

In addition, the sides of the slots are sized so they are just a littlewider than standard off-the-shelf hex nuts of the size appropriate formounting to data center racks.

Some fastener types that this improved “T” slot system can accommodate,but are not limited to are listed below:

#10 × 32 Hex Head bolt 202 #10 × 24 Hex Head bolt 202 M5 × .8 mm MetricHex head bolt 202 #8 × 24 Hex Head bolt 202 #8 × 32 Carriage head bolt203 #8 × 32 Standard round head screw with washer 204 #10 × 24 Standardround head screw without washer 204 Hex Nut, #8 and #10 205, 206 #8 × 32flat head screw and washer 207 #8 and #10 Allen or Spline socket tipscrews (non-standard) 209 #8 and #10 Torx socket tip screws(non-standard) 210 #8 and #10 slotted tip screws 211

The ability to utilize a wide variety of mounting hardware styles, alongwith the slots being the full length of the enclosure, and the includedribs that prevent round head and flat head screws from turning inside ofthe slot make mounting this product versatile and convenient.

FIG. 14 shows the general principal components of one relay contactoperation authentication detection 400 that comprise the Relay OperationAuthentication Detector section of the MINI ATS.

AC power 212 is present always on the armature of the relay 211. When acommand from the Digital Control Electronics is initiated through the GKRelay Control 210 the relay 211 will move the armature to the SwitchedHigh Voltage output leg 213 of the relay 211. This is the normal powerpath for operation of the relay switch. There are four such switches inthe Mini ATS that comprise switching of the Hot and neutral (orsecondary Hot) of the A side, and the Hot and neutral (or secondary Hot)of the B side.

The relay contact detection circuitry consists of a very small pulsetransformer 214 designed to operate at low voltages, such as 5 voltsconnected across the armature of the relay 211 and the unused normallyclosed contact 217 of the relay 211. The windings 216 of the pulsetransformer 214 are thereby normally shorted out by the normally closedposition of the relay 211 when it is not actuated and no power is beingsent through the relay from the input 212 to the output 213.

At all times, a small 400 Kilohertz (KHz) oscillator 215 is operating.This frequency can be anything appropriate to the characteristics of theselected pulse transformer 214 and could vary from various applicationsto another. For the use in the MINI ATS, a transformer that operateswell at 400 KHz is selected due to its small size and efficiency. Theoutput of the oscillator 215 is connected to the pulse transformer 214through a current limiting resistor 220. Thus, when the set of windings216 are shorted due to the position of the contacts of the relay 211,the windings of the oscillator connected side of the transformer 219 arealso shorted out. Most of the output power of the oscillator 215 isdissipated in the current limiting resistor 220. Subsequently, thewindings of the pulse transformer 218 that are connected to the bridgerectifier 221 have very little signal transmitted there also. Thus, novoltage is developed across the capacitor 222 and the bleed downresistor 223. The voltage output at 224 is essentially zero. Thus, azero-output voltage represents that the relay 211 contacts are in theopen condition with regards to the power path.

When a command from the Digital Control Electronics is initiated throughthe GK Relay Control 210 the relay 211 will move the armature to theSwitched High Voltage output leg 213 of the relay 211 and thus removethe short condition on the winding of the transformer 216 the momentthat the armature of the relay 211 leaves the contact 217 when the coilof the relay is energized. When the short condition on the winding 216is removed, the oscillator 215 output can now energize the input windingof the pulse transformer 219 and the 400 KHz will be transmitted throughthe pulse transformer 214 to the output winding 218. The AC will berectified in the bridge rectifier 221 and filtered by the capacitor 222.Thus, an output voltage represents that the relay 211 contacts are ontheir way to or at the closed condition with regards to the power pathand allowing the relay to pas power from the input 212 to the output213. The selection of the winding ratio and the operational voltage ofthe oscillator 215 determine the output voltage of the bridge rectifier221. In this instantiation the output voltage selected is 5 volts and isdirectly compatible with the electronics in the Digital ControlElectronics.

A bleed down resistor 223 is connected across the filter capacitor 222to deplete the voltage there when the output of the pulse transformer214 ceases to deliver voltage due to a short condition returning to therelay 211 contact closure where it is connected to the Normally Closedcontact 217. This bleed down is very fast since the filter capacitor isselected to be only big enough to ensure consistent output voltageduring the transition from positive to negative on the output of thetransformer 214.

When the command from the Digital Control Electronics to disconnect theAC power path through the relay 211 occurs, the relay armaturetransitions from the Normally Open contact position 213 to the normallyclosed contact 217. For the pulse transformer relay switch positionsense winding 216 to become shorted out and thus signal successfulcompletion of opening of the power path, the armature must physicallybecome disconnected from the output. This increases the reliability ofaccurately detecting the state of the relay.

In addition, because the transformer is connected only to the unusedNormally Closed contact 217, the circuit operates efficient andautonomously from whatever voltages or frequencies are present on thepower path.

FIG. 15A shows the basic block diagram of the Mini ATS now including theRelay Operation Authentication Detectors 301, 302, 303 and 304. It showsthe device with no input to output connections such as would be the offcondition of the Mini ATS. Note that there is no power path shownconnected from either input to the output. Also note that the output ofeach of the Relay Operation Authentication Detectors is represented byan L, for Low, or no voltage from the detectors within each RelayOperation Authentication Detector section. Each of the four RelayOperation Authentication Detector relays are now in the Normally Closedposition (non-energized) states, and thus the contact sense windings ofall four are shorted.

In normal operation, one or the other of the inputs will be connected tothe output. FIG. 15B shows that, in this case, the input “A” isconnected to the output “OUT”. Now, each of the outputs of the RelayOperation Authentication Detectors associated with the “A” side 301 and302 are now outputting a high signal represented by an H for each. Thishi signal is sent to the Digital Control Electronics where it can verifythe state of the relays and can continue to operate normally. Eachchange of state commanded by the Digital Control Electronics can bemonitored and authenticated by the Digital Control Electronics in thismanner.

FIG. 15C shows a possible fault condition where the Digital ControlElectronics is commanding the A side Gate Keeper relays to disconnectvia the Gate Keeper Amplifier 91 by turning off power to the relay. Butthe Normally Open contact on the Hot side is shown diagrammatically asbeing “stuck” to the output connection. The complementary relay hassuccessfully opened. Thus, the output from the Relay OperationAuthentication Detector for that relay contact remains in the “High”state, thus signaling the Digital Control Electronics that the operationto disconnect that relay contact has failed. This allows the DigitalControl Electronics to take appropriate steps and not apply power to theGate Keeper amplifier on the B side thus potentially causing a hazardousshort of the A side to the B side.

It is possible now for the Digital Control Electronics to repeated turnon and off the affected relay and monitor the state of that RelayOperation Authentication Detector. It is possible, even likely thatrepeated operation of the relay will eventually cause the stuck contactsto dislodge. The unit reliability is subsequently improved by thisself-healing potential of this design.

FIG. 16 shows several methods for increasing the uptime andmaintainability of an SBC module that is acting as the control moduleeither standalone or as part of a larger device. Several of the ATSinstantiations described herein can be used to eliminate power-relateddowntime. It allows single power supply SBC modules and other criticalloads to be fed by both filtered utility line power and a UPS, or twoUPS units, with either as the primary or backup power source. Ifpossible, the UPS can be plugged into a different branch circuit thanthe second input to the μATS™, allowing the UPS to be taken out ofservice for maintenance or testing without SBC downtime. With thisconfiguration, both the utility line power and the UPS must fail at thesame time to result in downtime. The figure below compares thetraditional methods of powering an SBC module to those possible with asuitable ATS.

FIG. 16A shows one possible instantiation of a novel circuit to activatethe inrush limiting function that can be used in ATS units, as describedin this filing or other possible ATS instantiations.

The sub-assembly 500 is comprised of a relay 506 in the path of the ACpower that exits the ATS. The power that is delivered to the output ofthe uATS or the Industrial uATS must pass through this relay. Across theinput 505 and the output 507 of the relay 506 is connected a low valueresistor 512, approximately 10 ohms. This resistance can be fixed, or itcan be of a Negative Temperature Coefficient (NTC) type usedspecifically for inrush applications. In the case of the Zonit uATS andZonit Industrial products, this resistor is of the NTC variety, and is10 ohms.

Since the intent of the inrush limiter is to limit the peak current atthe moment of the transfer from one source to the other source and thenbecome transparent, the circuit relies on the electronic drive circuitsin those products that change the state of the relays that direct thepower within the ATS. The signal to the Gate Keeper relays within theATS can be used to signal this Inrush limiter circuit to operate. Whentransferring to the alternate power source in the ATS, a drive signal of12 to 48 volts is applied to a steering relay, known as a Gate Keeper orGK relay. When the transfer is back, the signal to that GK relay isremoved and the relay then connects the AC power to the original source.In other words, the drive to the GK relay inside of the ATS product canbe used to actuate this inrush limiter circuit 500 for both transitions.At the moment of the transfer, either direction in the ATS product, thisinrush limiter circuit actuates its relay 506 momentarily to bypass theAC power through the limiting resistor 512. After a short period oftime, 20 to 100 milliseconds in the case of uATS and uATS Industrialproducts, the relay 506 is de-energized and the Normally Closed (NC)contacts again pass the power from the input 505 to the output 507, thusbypassing the internal limiting resistor 512.

The signal from the ATS product that actuates GK relays is directed tothe input of the Inrush Limiter Circuit from connection 514 throughlimiting resistor 501 and capacitor 502 to the three transistors 508,509 and 515. If the transition is positive going, current is directed tothe base of Q508 and blocked by the reverse emitter of Q509. In thatcase, Q508 is turned on for a period of time determined by the dischargerate of the capacitor 502 and the limited current from resistor 501.These components are selected to supply adequate turn on current in Q508 for a period of about 30 milliseconds before the capacitor chargesup adequately to stop presenting current to the base of Q 508, thusallowing it to turn off. While Q 508 is in the on condition, thecollector of Q 508 is pulled to the emitter voltage, turned ON so tosay. The low going pulse on the collector of the transistor 508 iscoupled through the coupling capacitor 504 to the relay 506 coil 511thus turning that relay on, and actuating the armature of the relay 506,and disconnecting the short across the inrush limiting resistor 512. ACpower must now pass from the input of the inrush limiter circuit 505 tothe output 507 via the inrush limiting resistor 512. After a period ofabout 30 milliseconds, the charge that was stored in the couplingcapacitor 504 is nearing depletion, but at that time the drive signalfrom the transistor 508 turns off, thus releasing the drive to the relay506. At this time, the coupling capacitor is discharged, and now beginsrecharging through the charge limiter resistor 503 from an internal DCpower supply located in the main ATS unit. This method of powering therelay is novel in that it only stores enough energy to actuate the relayfor the desired time period, about 30 milliseconds in this case. Andthis configuration also takes advantage of the fact that after atransfer, the main ATS device will pause for a minimum of about 3 to 5seconds before another transfer is initiated. This allows the couplingcapacitor ample time to recharge slowly in preparation for the nextinterruption cycle. This imposes very little drain on the main powersupplies of the ATS itself. Those power supplies are designed to operateat the very minimum power needs of the main ATS product and were notdesigned to drive an additional relay directly. Not utilizing the novelpower circuit of this invention would impose excessive power draw on themain power supply and possibly affect normal operation of the ATS. Thisdesign allows for this circuit to be added to the existing design withlittle modification to those products other than tapping into the GKrelay drive for signaling, connection to the power supply and insertingthe relay 506, and resistor 512 in the power path exiting the ATSdevice.

When the input signal to the inrush limiter circuit 500 goes from thehigh state to the low state as in the case where the main ATS unit istransferring back to the original source, the falling voltage at theinput to the inrush limiter is coupled via connection 514 throughcurrent limiting resistor 510 and coupling capacitor 502 to the threetransistors 508, 509 and 515. In this case, the falling signal tries togo negative and is blocked by the reversed biased base of 508 thus fullyshutting it off. Now, the negative going pulse from the couplingcapacitor 502 causes forward conduction through the emitter of thenegative translation detection transistor 509 from its base which isgrounded. At this point the negative transition detection transistorturns on and the collector is pulled towards ground. It is connected tothe base of relay drive transistor two 515, which is configured in anemitter follower current amplifier connection to the coupling capacitor504. Again, as in the opposing scenario, the current through thetransistor 515 actuates the armature of the relay 506 and disconnectingthe short across the inrush limiting resistor 512. AC power must nowpass from the input of the inrush limiter circuit 505 to the output 507via the inrush limiting resistor 512. After a period of about 30milliseconds, the charge that was stored in the coupling capacitor 504is nearing depletion, but at that time the drive signal from thenegative translation detection transistor 509 turns off, thus releasingthe drive to the relay 506. At this time, the coupling capacitor isdischarged, and now begins recharging through the charge limiterresistor 503 from an internal DC power supply located in the main ATSunit in preparation for the next interrupt cycle.

In yet another example instantiation of the invention, FIGS. 16B-16Hshow an example instantiation of the invention that can be created fromthe methods and apparatus described herein (Zonit μATS-IND™). A keypoint in this instantiation is that the use of current limiting methodsallows the automatic transfer switch to be designed to transfer withoutregard to the potential difference between the A-B inputs because thecurrent limiting technology prevents damaging arcs from forming acrossthe relays in the ATS during a transfer event. This protects the relaysfrom arc damage and possible micro-welding and simplifies the design ofthe ATS unit, since it does not have to (but could if desired) transferon a zero crossing of the AC cycle on a secondary source to primarysource transfer. The sample instantiation places current limiting on theoutput of the ATS, but it can be placed on one or more of the A input,the B input, or the output as is best suited for the particularapplication. Some of these options are described in other parts of thisand associated filings.

It should be noted that the circuits described in this and the otherinstantiations herein can be greatly compressed as to parts count,spaced used, and power consumed by designing ASIC chips to implementthese same or substantially same circuits. This is valuable whendesigning to the minimum form-factor possible, which is useful in thedata center market, where space in the rack is at a premium. Thecreation of ASIC chips does require significant investment.

Inrush Limiting

The primary function of an ATS is to select between two independent ACpower sources, henceforth called A source and B source, and connect theselected source to the output connector. The ATS can be designed to usea preferred source that it will go to if both of the sources areavailable. In this example instantiation the preferred source for theATS is the A source.

The ATS can operate from sources of different phases also. The useroften does not know what phase of the AC line is present on eachavailable source power, thus it is desirable that the ATS be able tooperate with any phase combination or polarity of the input sources.

The ATS is designed so that the A source and the B source are neverinadvertently connected together. Because the A source and the B sourcecan have differing phases or polarities, it is possible to have currentflow between the sources in the event of a failure of the switchingcomponents of the ATS. For this reason, a means of separating the twosources is required. This is generally accomplished by utilizing anelectro-mechanical relay with a physical armature, or moving element,that selects between one electrical contact, or another. A physicalseparation thus exists between the two power sources so only one can beconnected at any one time. One method of doing this is commonly referredto as relays, and in the case of the example ATS this relay will bereferred to as the “gatekeeper” relay.

However, to make the transfer of power from one source to the other beable to occur relatively quickly, the distance between the contacts ofthe relays must be kept to a minimum, and the weight of the armaturemust also be kept to a minimum. The lowered inertia of the movingcomponent, the armature, coupled with the minimized gap between theselected contacts allows for maximizing the speed of a transfer from onesource to another. This is valuable because many of the intendedapplications for the ATS are usage cases where even short power outagescan cause the equipment connected to the output of the ATS to power downor reset, causing downtime. Thus, fast transfers between sources iscritical, and is one of the unique aspects of the invention.

Issues can arise when using relays with characteristics that result infast transfer times, such as small gaps between their contacts. In theevent of an overload condition happening on the output of the ATSoccurring at the same time a transfer occurs, the overload current couldcause an arc to develop across the two contacts that are separating(disconnecting) that could become long enough to still be sustained whencontact with the opposite side occurs. In this case, the arc would thenbe sustained between the two differing phases of the two inputs. The arcwould become a nearly zero ohm short between the two inputs in that caseand serious damage could occur. Of course, circuit breakers and fuses inline with the inputs would protect the circuit, but the momentary shortcircuit could cause unintended damage to the relays, other components inthe ATS, connected circuits, equipment or even physical electricalconnections. To prevent this condition, a method of limiting the peakelectrical current to a threshold that is below the sustained arcpotential of those contacts connected to the input sources is verydesirable. This limitation of current can be in the connection betweenthe gatekeeper relay and the output because that is the only possiblesource of the potential concurrent high current load and the inputpower. Thus, placing a means of limiting the current in that output canmitigate the problem of arc formation between the contacts of the inputsources. The methodology to perform this mitigation the ATS isdesignated “inrush limiter” and the inrush limiter has another function,albeit still controlling potentially excessive current during thetransfer event.

Often, the equipment connected to the output of the ATS has loadcharacteristics that are not purely resistive. It can be inductive, orcapacitive, or a combination of both. In any case of electrical loadshaving these inductive or capacitive characteristics, it is referred toas “reactive.” Currents can flow between the source and the load thatare not proportional to the voltage at any given time. In the case ofmany loads, a capacitance is place across the AC power to minimize theRadio Frequency (RF) interference. Or the load could be a transformer,which will introduce Inductive Fly-back, often with severe currentsassociated with the flyback.

The reactive loads can momentarily generate very high currents relativeto the operating current. The operating current is what the design ofthe ATS internal components is generally specified to meet. One possiblesolution for making the ATS immune to the excessive currents is toutilize components that are designed for these much higher currents.However, larger mechanical relays result in much slower transfer times(which may make the ATS unsuitable for ensuring uninterrupted uptime forITE devices and other types of equipment or devices that have integrateddigital processors or other digitally based control mechanisms) and addsignificant size and cost to the finished product, both of which areundesirable.

An alternative to larger components is to provide a method of limitingthe maximum current during the time of the transfer. Then after thetransfer is complete, apply another mechanical switch that bypasses thatcurrent limiting component. This bypass eliminates the power lossassociated with a current limiting means.

Thus, the inrush limiting feature of the ATS described in this inventionis twofold. It mitigates the possibility of shorting the two sources andit mitigates the destructive potential of reactive loads.

Inrush limiting circuitry and functionality is described in U.S. patentapplication Ser. No. 16/817,504, entitled “Relay Conditioning and PowerSurge Control,” filed on Mar. 12, 2020 and incorporated herein byreference. That filing describes several types of loads that are foundin the data center and other environments that can cause high levels oftransient currents. It also describes some innovative methods andapparatus to deal with those issues in the design and construction ofATS and other types of electrical equipment.

Fast Response to A Source Power Failure

A critical feature of the ATS is its ability to rapidly detect a failureof the AC power and initiate the transfer from the failing source to thealternate source a quickly as possible. The period of time to make thisdecision must be slightly greater than an average power line short timeoutage, such as less than 2 to 4 milliseconds (ms). A commonly usedmetric of a power source disruption versus a power source outage is thatanything loss of power that lasts longer than 4 milliseconds is anoutage, anything less is a brief disruption. These momentary poweroutages are common and would cause unnecessary transfer events if theywere not acted on properly. The ATS has a unique method of detecting theAC outage and filtering the momentary losses and rejecting them whilestill guaranteeing a quick transfer that is fast enough for ITE devicesand other microprocessor-based devices to stay up when a transfer isdetermined to actually be required, described below.

The power consumed by the circuits that operate within the ATS on the Asource side is passed through an optical coupler. Thus, when AC powerthat is valid is present on the A source, the optical detector is “on”and allowing the signal that says the AC power on the A source is good(A-OK) can pass to the B source side control electronics and keep itshut off, and the gatekeeper relay(s) un-energized and selecting the Aside input. The moment that power fails on the A side, the opticalconductor shuts off because the power is not passing to the electroniccomponents of the A side electronics. When the optical coupler shutsoff, the electronics on the B side no longer sees the signal that the Aside is good (A-OK false) then it initiates switching the gatekeeperrelay from the A source to the B source. This A side power faildetection circuitry is robust, and very fast. No complex circuitry isneeded to discriminate if the power is there or not. A simple RC filterallows selection of how long the outage must be to initiate thetransfer.

HIPOT Compliance and Safety Isolation

The ATS must be capable of withstanding a high impulse (or sustained)voltage between the A source and the B source for safety reasons.Depending on the country of use, the agency that defines the worst-caseresistance to impulse or sustained voltage will mandate up to 3750 voltsof “withstand” potential. In the event of high voltage appearing ateither the A source, or the B source, the ATS must be able to preventthe high voltage from becoming present on the opposite source. This iscommonly tested and verified by a test called the High Potential Test,or HIPOT.

Because the design of the ATS minimizes the size of the finishedproduct, and it also minimizes the transfer time by utilizing small, lowmass mechanical relay components, the voltage where the A source inputand the B source input power enters the gatekeeper relay has a gap thatcould break into an arc at these HIPOT voltages. Thus, an auxiliaryrelay set of gaps is inserted in the A source input power path. The sumof the distances of both the gatekeeper relays and this added A sourceinput relay (A disconnect relay) results in achieving the necessary gapto prevent the HIPOT voltage from causing a breakdown, and thus achievesagency specified voltage threshold immunity.

There are six basic states the ATS can be in at any given time.

-   -   1. Both Sides Powered, On Preferred Side A    -   2. A Side Fails, Transfer to B side Initiated    -   3. Transferred to the B Side, Output Power through Current        Limiter    -   4. On B Side, Current Limiter Bypassed    -   5. On B Side, A Side Power has Returned and Transfer from B Side        to A Side has Initiated    -   6. Transferred to the A side, Output power through the Current        Limiter

Description of Circuit Functionality

Observe FIG. 16B. Power is present on Both the A Side 1601 and the Bside 1602 inputs. AC power is following the Red Path through the CircuitBreaker CB 1603 to the normally closed input contacts of the gatekeeperrelay. Because the Gatekeeper Relay is de-energized, the armature is inthe select A Side position and it conducts the AC Power to the load 1605via the contacts in the normally closed Inrush Limiter Relay 1606. Thisis the normal operating condition of the ATS.

AC power present at the A Source input is also directed to the A side ACto DC Power Supply 1607 at this time. The current supplied by the powersupply 1607 passes through the A Disconnect Relay 1612 coil andenergizes the relay. The current also passes through the optical coupler1608 causing the output of the optical coupler to conduct as well. Withpower applied to the coil of the A Disconnect Relay 1612, the contactsare in the closed position shown and conduction power through the relayand to the Gatekeeper Relay 1604.

The output of the optical coupler 1608 conducting allows DC current fromthe B side AC to DC Power Supply 1609 to be switched off and not allowedto flow to the coil of the Gatekeeper Relay by the electronic switch1611. Thus, the Gatekeeper Relay 1604 is off and allowing the A side ACpower 1601 to pass through to the output and the Load 1605.

FIG. 16C shows the electrical path shortly after the A Source AC Power1601 has ceased. At this point, AC B Source power, is supplied to the Bside Ac to DC power supply 1609 via the Circuit Breaker CB 1615. Poweris available to energize the electronic switch 1611. Because power hasfailed on the A Source 1601, there is no power to flow through theoptical coupler 1608, and thus the output to the optical coupler 1608 isnot conducting. When the output of the optical coupler 168 is notconducting the electronic switch 1611 turns ON and conducts DC powerfrom the B side AC to DC power supply 1609 through the coil of theGatekeeper Relay 1604 1 or 2 ms after the Gatekeeper Relay 1604 coil isenergized, the armature starts to move off of the Normally Closed (NC)contacts and disconnects the A Side input 1601 power path from the load1605. In addition, the A Disconnect Relay 1612 is also starting todisconnect. The power to the load 1605 is disconnected completely atthis time. In addition, at the moment that the electronic switch 1611changes state, a signal is sent to the Inrush Control Timer 1613. TheInrush Control Relay 1606 is energized and the Normally Closed contactsbegin to open. This is important timing. The Inrush Control Relaycontacts must be open prior to closure of any of the AC power pathcontacts so that any power that flows then will be forced to passthrough the Inrush Limiter Resistor 1614. Presently, with the armaturesof all three relays in flight, there is no current presented to the Load1605. The stage is set for when the current path is restored, forcurrent to pass through the Inrush Limiter Resistor 1614.

FIG. 16D shows the state of the ATS during the period between 2 ms afterthe Loss of A Source 1601 power and up to about 40 ms later. During thisperiod of time any reactive load current or voltage that may occurduring the transfer cycle from A source to B source will have had topass through the Inrush Limiting Resistor 1614. The value of thisresistor is calculated to provide substantial current to the Load 1605,but excessive current will dissipate as heat in the Inrush LimiterResistor 1614. The use of an Inrush Limiter Resistor is not unique, butthe means of actuating the bypass around it is.

FIG. 16E shows the steady state of the ATS after about 40 ms after theloss of power to the A Source 1601. The Inrush Control Timer 1613 hasbeen on for a period exceeding its timeout parameters, in this case 40ms. This value can be adjusted easily for optimum performance, but the40 ms is presently selected because it guarantees that any transientevents that could be destructive to the relay contacts has passed, aswell as any arc potential from the load being carried between contactsof the Gatekeeper Relay 1604. Since the Inrush Control Timer 1613 hastimed out, the current to the Inrush Control Relay 1606 contacts havereturned to the Normally Closed (NC) condition and current can passthrough the relay on its way to the Load 1605.

In addition, after about 4 or 5 ms of the initiation of the transfer,the A Disconnect Relay 1612 has been powered off long enough to be fullyopen. In addition, the Gatekeeper Relay 1610 has been energized longenough that the contacts are now closed in the position that conducts ACpower from the B Source input 1602 via the Circuit Breaker CB 1615, tothe Load 1605 through the Inrush Limiter Relay 1606, bypassing theInrush Limiter Resistor 1614.

At this point, as long as there is no power present on the A Source 1601power will be delivered to the Load 1605 from the B Source 1602. This isthe steady state for the condition of A source off, B source On.

FIG. 16F shows the state of the ATS about 2 to 4 seconds after the ACpower is returned to the A Source 1601 input. Immediately after thereturn of power to the A Source 1601 the AD to DC Power Supply 1607becomes powered on, and the voltage present is detected as being in anacceptable range by the Under and Over Voltage Detector 1616, a timercircuit

Return to A side Delay 1617 is started. It operates for about 2 to 4seconds, inhibiting the current from the AC to DC Power Supply 1607 frompassing through the input of the optical coupler 1608 and the coil ofthe A Disconnect Relay 1612. This is the delay after AC power returns tothe A Source to allow that power to settle down and for any minorinterruptions to dissipate. After the 2 to 4 seconds has elapsed, thetimer has expired and current is allowed to flow through the coil 1618of the A Disconnect Relay 1612, thus energizing it, and through theinput to the optical coupler 1608, thus turning on the output of theoptical coupler 1608. The A disconnect Relay 1612 starts to move towardsconnection but is not yet there. Simultaneously, the current from the Bside AC to DC Power Supply 1609 is allowed to flow through the output ofthe optical coupler 1608 and through the electronic switch turning offthe switch 1611. This in turn disconnects power from the coil of theGatekeeper Relay 1604. The contacts in the Gatekeeper Relay begin tomove, but are not connected to the opposite side yet, thus preventingany AC power to pass through the ATS to the Load 1605.

In addition, at this time, the Inrush Control Timer 1613 has seen thetransition from off to on in the current path through the electronicswitch drive circuit 1611 and the Inrush Control Timer has energized. Itwill remain energized for about 40 ms. The Inrush Control Relay 1606 isnow energized and the Normally Closed contacts begin to open. Again,this is important timing. The Inrush Control Relay contacts must be openprior to closure of any of the AC power path contacts so that any powerthat flows then will be forced to pass through the Inrush LimiterResistor 1614. Presently, with the armatures of all three relays inflight, there is no current presented to the Load 1605. The stage is setfor when the current path is restored to the A Source 1601, for currentto pass through the Inrush Limiter Resistor 1614 for a period of about40 ms. Thus, dissipating any possible transient voltage and currentspikes that might occur.

FIG. 16G shows the state of the ATS during the period about 2 ms. afterthe initiation of return to A Source 1601 power and up to about 40 mslater. At this point the Inrush Control Timer has not expired and theInrush Limiter Relay 1606 remains open. During this period of time anyreactive load current or voltage that may occur during the transfercycle from B source to A source will have to pass through the InrushLimiting Resistor 1614. The value of this resistor is calculated toprovide substantial current to the Load 165, but excessive current willdissipate as heat in the Inrush Limiter Resistor 1614.

FIG. 16H shows the steady state condition described for FIG. 16B. ACPower is in Steady State on the A Source, the Inrush Control Timer 1613time has expired and the Inrush Control Relay 1606 has returned to theclosed position.

FIG. 17 shows an example instantiation of a high definition (HD)waveform sensor circuit. The key design constrains are small size, lowenergy usage and very low cost, which is novel, because it enables largenumbers of HD waveform sensors to be very widely deployed and thatinformation to be gathered and analyzed. This in turn enables many typesof status, diagnostic and predictive analysis for the power distributionsystem and connected devices, many details of which are described in theZonit cases. The inventions described in the Zonit cases (e.g., powersignal signature recognition) can incorporate this high-definitionsensor capability for detecting and reporting high resolution (forexample 0-100 kHz sampling rates, note zero Hz is DC power) waveformsampling to measure power quality parameters, for example Voltage andCurrent information regarding the AC power lines that the variousdevices are connected to both for their inputs and outputs. It can alsobe incorporated into any of the Zonit inventions referenced herein andalso implemented in a plug-in module or other convenient form-factor(many of which are described herein) and include provisions to storeand/or communicate the waveform information to other devices via avariety of communication methods, such as wireless, USB, Ethernet andothers. These requirements have resulted in the creation of aspecialized set of circuits that perform the required function.

The measurement of these AC lines require very high voltage isolationfrom the digital and analog circuits for safety reasons. Isolation inexcess of 3000 VAC is often necessary. In addition, small size isimportant in the Zonit products, as well as efficient operation. Thehigh isolation buffer/amplifier shown in FIG. 600 consists of an ACpower path through the buffer consisting of the AC Line in 601, to theAC Line out 619 via a Hall Effect current sense chip 615.

AC power generally also supplies AC power into the power supply 605 thatgenerates a DC output that is isolated from the AC mains. The DC outputdrives the output amplifiers that are connected to the digital andanalog sub-circuits that are external. The isolated DC output 603 isalso routed to another High Isolation power supply 607 which in turnsupplies the input of the voltage buffer 613 allowing the DC input tohave a reference to the AC Line 620.

For Voltage detection, the AC line 601 is connected to the precisionrectifier 608 to generate a rectified DC output with no filtering fordetection. The output of the rectifier is referenced to the AC line 620.The input of the High Isolation buffer amplifier 613 is referenced tothe same AC line, 620. The High Isolation buffer amplifier 613 input 612detects the output of the voltage dividing resistors 610 and 611. Thehigh isolation buffer amplifier 613 then outputs a rectified and scaledSensed Voltage Output 617 to the external measurement electronics.

For Current detection, the AC current is passed through the input 616 ofa Hall Effect current sense chip 615 where the faint magnetic field 614is detected across a High Isolation voltage barrier. The Sensed Currentoutput 618 of the Hall Effect magnetic detector 616 is routed to theexternal measurement electronics. FIG. 18 shows a perspective view ofone possible instantiation of a Zonit μATS-INDUSTRIAL. This sameform-factor can be used for a Zonit μATS-V2 or other ATS instantiations.

The foregoing description of the present invention has been presentedfor purposes of illustration and description. Furthermore, thedescription is not intended to limit the invention to the form disclosedherein. Consequently, variations and modifications commensurate with theabove teachings, and skill and knowledge of the relevant art, are withinthe scope of the present invention. The embodiments describedhereinabove are further intended to explain best modes known ofpracticing the invention and to enable others skilled in the art toutilize the invention in such or other embodiments and with variousmodifications required by the particular application(s) or use(s) of thepresent invention. It is intended that the appended claims be construedto include alternative embodiments to the extent permitted by the priorart.

What is claimed:
 1. An automatic transfer switch system, comprising; aswitch unit having a first input for receiving a first power signal viaa first power cord extending between said switch unit and first poweroutlet associated with a first power source, a second input forreceiving a second power signal via a second power cord extendingbetween said switch unit and a second power outlet associated with asecond power source, an output for providing a power signal to aconnected load, and a switch for selectively connecting one of saidfirst and second inputs to said output depending on a power signalstatus of at least one of said first and second power signals; anoptical coupler device for sensing said power signal status; and a powersurge managing circuit, responsive to said optical coupler device, formanaging power surges at said switch unit, said power surge managingcircuit being disposed at at least one of: 1) between said switch unitand one of said first and second power outlets, and 2) between saidswitch unit and said load.
 2. The switch system of claim 1, wherein saidswitch comprises a switch relay for selectively connecting one of saidfirst and second inputs to said output and said power surge managingcircuit includes a gatekeeper relay disposed in series with said switchrelay.
 3. The switch system of claim 2, wherein said optical couplerdevice is operative to detect a power event in relation to said firstpower signal, said power event being one of a power outage and a powersignal degradation.
 4. The switch system of claim 3, further comprisinga control element, associated with said optical coupler device, fordistinguishing between transient power events, where cycling of saidswitch is not desired, and persistent power events where cycling of saidswitch is desired.
 5. The switch system of claim 4, wherein said controlelement comprises an RC filter.
 6. The switch system of claim 1, whereineach of said first and second power cords includes a first end forconnecting to said switch unit and a second end for connecting to one ofsaid first and second power and said power surge managing circuit isdisposed at least in part in-line on one of said first and second powercords between said first and second ends.
 7. The switch system of claim1, wherein said switch unit is configured such that said first powersource is a primary power source of said switch unit and said powersurge managing circuit is disposed at least in part between said switchunit and said second outlet.
 8. The switch system of claim 1, wherein atleast one of said first and second outlets is an outlet of a powerstrip.
 9. The switch system of claim 1, wherein said switch unit isoperative for switching from a first state, wherein said first input isconnected the said output, and a second state, wherein said second inputis connected to said output, in response to detecting one of a poweroutage and a degradation of said first power signal from said firstpower source.
 10. The switch system of claim 1, wherein said switchcompromises a first electromechanical relay.
 11. The switch system ofclaim 1, wherein said switch compromises a solid-state switch.
 12. Theswitch system of claim 1, when said switch unit and said power surgemanaging circuit are disposed in said switch housing.
 13. A method foroperating an automatic transfer switch system, comprising; providing aswitch unit having a first input for receiving a first power signal viaa first power cord extending between said switch unit and first poweroutlet associated with a first power source, a second input forreceiving a second power signal via a second power cord extendingbetween said switch unit and a second power outlet associated with asecond power source, an output for providing a power signal to aconnected load, and a switch for selectively connecting one of saidfirst and second inputs to said output depending on a power signalstatus of at least one of said first and second power signals; operatingan optical coupler device for sensing said power signal status; andoperating a power surge managing circuit, responsive to said opticalcoupler device, for managing power surges at said switch unit, saidpower surge managing circuit being disposed at at least one of: 1)between said switch unit and one of said first and second power outlets,and 2) between said switch unit and said load.
 14. The method of claim13, wherein said switch comprises a switch relay for selectivelyconnecting one of said first and second inputs to said output and saidpower surge managing circuit includes a gatekeeper relay disposed inseries with said switch relay.
 15. The method of claim 14, wherein saidoptical coupler device is operative to detect a power event in relationto said first power signal, said power event being one of a power outageand a power signal degradation.
 16. The method of claim 15, furthercomprising providing a control element, associated with said opticalcoupler device, for distinguishing between transient power events, wherecycling of said switch is not desired, and persistent power events wherecycling of said switch is desired.
 17. The method of claim 16, whereinsaid control element comprises an RC filter.
 18. The method of claim 13,wherein each of said first and second power cords includes a first endfor connecting to said switch unit and a second end for connecting toone of said first and second power and said power surge managing circuitis disposed at least in part in-line on one of said first and secondpower cords between said first and second ends.
 19. The method of claim13, wherein said switch unit is configured such that said first powersource is a primary power source of said switch unit and said powersurge managing circuit is disposed at least in part between said switchunit and said second outlet.
 20. The method of claim 13, wherein atleast one of said first and second outlets is an outlet of a powerstrip.
 21. The method of claim 13, wherein said switch unit is operativefor switching from a first state, wherein said first input is connectedthe said output, and a second state, wherein said second input isconnected to said output, in response to detecting one of a power outageand a degradation of said first power signal from said first powersource.
 22. The method of claim 13, wherein said switch compromises afirst electromechanical relay.
 23. The method of claim 13, wherein saidswitch compromises a solid-state switch.
 24. The method of claim 13,when said switch unit and said power surge managing circuit are disposedin said switch housing.